{"title":"Baader Scientific \u0026 Photometric Filters","description":"\u003cp\u003eBaader Planetarium photometric filters let amateur and professional observatories collect calibrated brightness and colour measurements. Two standard systems are covered: Johnson-Cousins UBVRI and the Sloan Digital Sky Survey (SDSS) passbands.\u003c\/p\u003e\u003cp\u003eThe UBVRI filters are sold individually or as a set, as are the Sloan u', g', r', i', z-s' and y' filters with the complete ugriz' set. They are used for variable stars, exoplanet transits and asteroid lightcurves.\u003c\/p\u003e","products":[{"product_id":"baader-photometric-ubvri-filter-set","title":"Baader Photometric UBVRI Filter Set","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eStandardized UBVRI Bessel passbands for scientific photometry\u003c\/li\u003e\n\u003cli\u003eEnables measurement of variable stars, asteroids, and exoplanet transits\u003c\/li\u003e\n\u003cli\u003ePrecision polished substrates for wavefront integrity\u003c\/li\u003e\n\u003cli\u003eAdvanced anti-reflection coatings to maximize signal\u003c\/li\u003e\n\u003cli\u003eAvailable in multiple mounted and unmounted sizes\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n  \u003cdiv class=\"DAV-bg-light\"\u003e\n    \u003cdiv class=\"DAV-section-center\"\u003e\n      \u003ch2\u003eBaader Photometric UBVRI Filter Set\u003c\/h2\u003e\n      \u003cp\u003eThe Baader Photometric UBVRI Filter Set provides the 5 essential passbands required for serious scientific photometry. This set is engineered to conform to the Johnson-Cousins-Bessel standard, ensuring your measurements of variable stars, asteroids, or exoplanet transits are consistent and comparable with data from professional observatories worldwide. By isolating specific regions of the spectrum—from the near-ultraviolet (U) to the near-infrared (I)—this 5-filter set transforms your imaging rig into a scientific instrument capable of producing publishable data.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv class=\"DAV-bg-light\"\u003e\n    \u003cdiv class=\"DAV-section\"\u003e\n      \u003ch3\u003eThe 5-Filter UBVRI Bessel System for Scientific Measurement\u003c\/h3\u003e\n      \u003cp\u003eUnlike filters designed for aesthetic deep-sky imaging, this set is built for quantitative analysis. The U (Ultraviolet), B (Blue), V (Visual), R (Red), and I (Infrared) filters are designed with specific passbands defined by the Bessel system, the modern standard for stellar photometry. This standardization is critical; it allows your observations to be reliably transformed and compared against global databases like that of the American Association ofVariable Star Observers (AAVSO).\u003c\/p\u003e\n      \u003cp\u003eUsing these filters, you can precisely measure the brightness changes of celestial objects over time. This is the foundation for creating light curves that reveal the physical nature of eclipsing binary stars, the rotation period of an asteroid, or the dimming caused by a transiting exoplanet.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv class=\"DAV-bg-light\"\u003e\n    \u003cdiv class=\"DAV-section\"\u003e\n      \u003ch3\u003eSubstrate and Coating Integrity for Repeatable Data\u003c\/h3\u003e\n      \u003cp\u003eIn photometry, any variation in the filter can introduce errors into the data. Baader Planetarium filters are manufactured using optically flat, homofocal substrates, ensuring that refocusing is minimized when switching between the five filters. This maintains a consistent optical path and reduces a major source of potential systematic error during an observation run.\u003c\/p\u003e\n      \u003cp\u003eEach filter is treated with advanced anti-reflection coatings to suppress halos and maximize light transmission within its designated passband. This results in a higher signal-to-noise ratio, allowing for more precise measurements of faint targets or subtle brightness variations, which is the difference between a noisy light curve and a clean detection.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n\u003c\/div\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the Baader Photometric UBVRI Filter Set primarily used for?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThis filter set is a specialized tool for \u003cstrong\u003escientific photometry\u003c\/strong\u003e, not for creating color images. Its purpose is to accurately measure the brightness of celestial objects through standardized passbands. This allows amateur and professional astronomers to study variable stars, measure asteroid rotation periods, detect exoplanet transits, and contribute data to scientific organizations like the AAVSO.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the \"Bessel\" standard mean for these Baader UBVRI filters?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe \u003cstrong\u003eJohnson-Cousins-Bessel system\u003c\/strong\u003e is a set of standard photometric passbands used by astronomers globally. By adhering to the Bessel standard, the Baader UBVRI filters ensure that the data you collect is consistent and comparable with measurements made by other observers around the world. This is crucial for collaborative research and for submitting your observations to scientific databases.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I choose the right size for my Baader Photometric Filter Set?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe correct size depends entirely on your filter wheel and camera setup.\n      \u003c\/p\u003e\n\u003cul\u003e\n        \u003cli\u003e\n\u003cstrong\u003e1.25\" and 31mm:\u003c\/strong\u003e Common for smaller sensors and filter wheels where vignetting is not a concern.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003e36mm:\u003c\/strong\u003e A popular size for many dedicated astronomy cameras with APS-C or smaller sensors, offering a good balance of size and illumination.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003e2\" and 50mm (Round\/Square):\u003c\/strong\u003e Necessary for cameras with full-frame (35mm) or larger sensors to prevent the filter from blocking light at the corners of the field.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003e65x65mm and 100x100mm:\u003c\/strong\u003e Reserved for professional-grade systems with very large format CCD or CMOS sensors.\u003c\/li\u003e\n      \u003c\/ul\u003e\n    Check your filter wheel's documentation to confirm the required filter size and whether it accepts mounted or unmounted filters.\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader UBVRI filters for visual observing or standard LRGB imaging?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eNo, these filters are not suitable for those purposes. Visually, the U, B, and I filters will produce very dim or unusual views. For imaging, they are not a substitute for LRGB (Luminance, Red, Green, Blue) filters, which are designed with significant overlap to produce natural-looking color images. UBVRI filters have distinctly separate passbands designed for measurement, not aesthetic color reproduction.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Baader Photometric UBVRI set to measure the light curve of a star like Algol (Beta Persei)?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eTo measure the light curve of an eclipsing binary like \u003cstrong\u003eAlgol (Beta Persei)\u003c\/strong\u003e, you would typically use the V (Visual) filter, as most historical and comparative data is in this band. You would take a series of timed exposures of Algol before, during, and after its minimum brightness. Using photometry software, you would measure Algol's brightness relative to nearby, non-variable comparison stars in each frame. Plotting this measured brightness against time reveals the precise shape and timing of the eclipse, which is valuable scientific data.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eAre these Baader filters suitable for exoplanet transit photometry with an 11\" SCT?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eYes, absolutely. An 11\" SCT is an excellent instrument for exoplanet transit work, and this Baader filter set is ideal for it. For exoplanet transits, the \u003cstrong\u003eR (Red) or I (Infrared) filters\u003c\/strong\u003e are often preferred. These longer wavelengths are less affected by atmospheric scintillation, leading to more stable and precise measurements of the tiny dip in starlight as a planet passes in front of its host star.\u003c\/p\u003e\n  \u003c\/div\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" Mounted, 2\" Mounted, 31mm Unmounted, 36mm Unmounted, 50mm Unmounted, 50x50mm Square, 65x65mm Square, 100x100mm Square\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.03 (1.25\" Round Mounted)\u003cbr\u003e0.06 (2\" Round Mounted)\u003cbr\u003e0.02 (31mm Round Unmounted, 36mm Round Unmounted)\u003cbr\u003e0.07 (50mm Round Unmounted)\u003cbr\u003e0.10 (50x50mm Square Filter)\u003cbr\u003e0.16 (65x65mm Square Filter)\u003cbr\u003e0.39 (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e31 mm (31mm Round Unmounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Filter)\u003cbr\u003e65 x 65 mm (65x65mm Square Filter)\u003cbr\u003e100 x 100 mm (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eFilter-Set\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eCMOS, CCD, UBVRI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType of Filter\u003c\/td\u003e\n\u003ctd\u003eBandpass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eBessel-UBVRI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to Bessel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n  \u003cul class=\"DAV-grid\"\u003e\n  \u003c\/ul\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967358333213,"sku":"BAA-2961750","price":1018.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967358365981,"sku":"BAA-2961753","price":1515.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967358398749,"sku":"BAA-2961751","price":1114.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967358431517,"sku":"BAA-2961752","price":1231.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967358464285,"sku":"BAA-2961754","price":1667.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Filter","offer_id":44967358497053,"sku":"BAA-2961755","price":1784.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Filter","offer_id":44967358529821,"sku":"BAA-2961756","price":2126.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Filter","offer_id":44967358562589,"sku":"BAA-2961757","price":4776.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Baader-UBVRI-Filter-Set__28982.1635877141.1280.1280.jpg?v=1684341344"},{"product_id":"baader-photometric-ubvri-u-individual-filter","title":"Baader Photometric UBVRI-U Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eConforms to the Johnson-Cousins\/Bessel U-Band Photometric Standard\u003c\/li\u003e\n\u003cli\u003eDesigned for Scientific Photometry of Variable Stars and Stellar Classification\u003c\/li\u003e\n\u003cli\u003ePlaneoptically Polished Substrate for Zero Image Degradation\u003c\/li\u003e\n\u003cli\u003eLife-Coat™ Hard Coatings for Durability and Resistance to Aging\u003c\/li\u003e\n\u003cli\u003eAvailable in Multiple Formats from 1.25\" Mounted to 100x100mm Unmounted\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric UBVRI-U Individual Filter\u003c\/h2\u003e\n\u003cp\u003eThe Baader Photometric UBVRI-U Filter provides scientifically rigorous ultraviolet data by adhering to the Bessel U-band standard, available in research-ready formats from 1.25\" mounted to 100x100mm unmounted for consistent stellar classification and variable star observation. This is not an imaging filter for creating color composites; it is a scientific instrument for collecting precise, repeatable measurements of stellar brightness in the near-ultraviolet spectrum.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe U-Bessel Standard: Precision Ultraviolet Photometry\u003c\/h3\u003e\n\u003cp\u003eThis filter is designed to strictly conform to the U-band passband of the standardized Johnson-Cousins\/Bessel UBVRI system. This system is the bedrock of modern photometry, allowing astronomers worldwide to produce comparable data. The U-filter isolates a specific slice of the near-ultraviolet spectrum, critical for analyzing the hottest, most energetic stars and phenomena.\u003c\/p\u003e\n\u003cp\u003eBy using the Baader U-Filter, your measurements of O- and B-type stars, cataclysmic variables, or active galactic nuclei can be directly compared to professional datasets. It transforms your imaging setup into a tool for genuine scientific inquiry, enabling you to contribute to pro-am collaborations and long-term monitoring projects.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eResearch-Grade Optical Integrity for Data Stability\u003c\/h3\u003e\n\u003cp\u003eA filter's photometric accuracy depends on more than just its transmission curve; the physical substrate must be flawless. Each Baader Photometric Filter is made from a planeoptically polished substrate, ensuring it does not introduce any wavefront error to the optical path. The glass is perfectly homogeneous, guaranteeing consistent transmission across the entire field of view.\u003c\/p\u003e\n\u003cp\u003eTo ensure your data is valid for years to come, Baader employs advanced hard-coating techniques (Life-Coat™) that are dielectrically sealed at the edges. This process makes the coatings impervious to moisture and aging, preventing the bandpass from shifting over time—a critical requirement for any long-term variable star research.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003ePhotometric U-Filter vs. Standard UV\/IR Cut Filters: A Scientific Instrument\u003c\/h3\u003e\n\u003cp\u003eIt's crucial to understand the distinction between this photometric filter and a standard UV\/IR cut (Luminance) filter used for deep-sky imaging. A UV\/IR cut filter is designed for broadband transmission of the entire visible spectrum while blocking the unfocused ends. Its goal is to maximize signal for aesthetically pleasing images.\u003c\/p\u003e\n\u003cp\u003eThe Baader U-Filter does the opposite: it aggressively blocks all visible and infrared light to isolate only the scientifically valuable U-band. Using this for general imaging would result in a very dim, monochromatic image with low signal. Its purpose is not visual appeal but quantitative measurement, making it an essential tool for the serious amateur astronomer focused on data collection.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the Baader Photometric U-Filter primarily used for?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Baader Photometric U-Filter is a scientific instrument used for \u003cstrong\u003ephotometry\u003c\/strong\u003e—the precise measurement of starlight. Its primary applications include observing variable stars, classifying stars based on their color temperature (especially hot, blue O- and B-type stars), and studying energetic astronomical objects that are bright in ultraviolet light.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow is the Baader U-Bessel filter different from a standard UV\/IR cut filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA standard \u003cstrong\u003eUV\/IR cut filter\u003c\/strong\u003e is designed to pass the entire visible spectrum while blocking ultraviolet and infrared light, maximizing signal for color imaging. The \u003cstrong\u003eBaader U-Bessel filter\u003c\/strong\u003e does the opposite: it is designed to block all visible and IR light, passing only a very specific, standardized band of near-ultraviolet light for scientific measurement.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader Photometric U-Filter for visual observing or general astrophotography?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this filter is not suitable for visual use or for creating typical color astrophotos. Your eye is not sensitive to the ultraviolet wavelengths it passes, so everything would look dark. For imaging, it isolates such a narrow band of UV light that the resulting signal would be very low and not useful for creating a standard LRGB or narrowband image.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is it important that the Baader U-Filter is \"photometric\"?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003e\"Photometric\" means the filter's transmission curve strictly adheres to the established scientific U-Bessel standard. This ensures that brightness measurements you take can be accurately compared to data from other observers and professional observatories around the world. It guarantees your data is consistent, repeatable, and scientifically valid.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Baader Photometric U-Filter to study a variable star like Algol (Beta Persei)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYou would take a series of timed exposures of Algol using the Baader U-Filter with a monochrome camera. By measuring Algol's brightness relative to nearby, non-variable comparison stars in each frame, you can plot its light curve. The U-band is particularly useful for eclipsing binaries with hot stars like Algol, as it reveals temperature changes with high contrast.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI want to classify hot stars in the Orion Nebula (M42) with my 11\" SCT. Is the Baader U-Filter the right choice?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, it is the ideal choice. The hot, young O- and B-type stars of the Trapezium Cluster within M42 are extremely bright in ultraviolet light. By measuring their brightness through U, B, and V filters, you can calculate their color indices (e.g., U-B) and determine their spectral type and temperature with high accuracy, even from a backyard setup.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric Johnson-Cousins\/Bessel U-Band\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Unmounted)\u003cbr\u003e0.03 (65x65mm Square Unmounted)\u003cbr\u003e0.08 (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e31 mm (31mm Round Unmounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Unmounted)\u003cbr\u003e65 x 65 mm (65x65mm Square Unmounted)\u003cbr\u003e100 x 100 mm (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eCMOS, CCD, UBVRI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eUBVRI-U\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to Bessel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Baader_Planetarium_Cleaning_and_Maintenance_of_Optics_Manual.pdf\" target=\"_blank\"\u003e\u003csvg class=\"DAV-img-box\" viewbox=\"0 0 512 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"\u003e\u003cpath d=\"M0 64C0 28.7 28.7 0 64 0L224 0l0 128c0 17.7 14.3 32 32 32l128 0 0 144-208 0c-35.3 0-64 28.7-64 64l0 144-48 0c-35.3 0-64-28.7-64-64L0 64zm384 64l-128 0L256 0 384 128zM176 352l32 0c30.9 0 56 25.1 56 56s-25.1 56-56 56l-16 0 0 32c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-48 0-80c0-8.8 7.2-16 16-16zm32 80c13.3 0 24-10.7 24-24s-10.7-24-24-24l-16 0 0 48 16 0zm96-80l32 0c26.5 0 48 21.5 48 48l0 64c0 26.5-21.5 48-48 48l-32 0c-8.8 0-16-7.2-16-16l0-128c0-8.8 7.2-16 16-16zm32 128c8.8 0 16-7.2 16-16l0-64c0-8.8-7.2-16-16-16l-16 0 0 96 16 0zm80-112c0-8.8 7.2-16 16-16l48 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 32 32 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 48c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-64 0-64z\" fill=\"#0047a7\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Planetarium Cleaning and Maintenance of Optics Manual\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967358693661,"sku":"BAA-2961750U","price":231.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967358726429,"sku":"BAA-2961753U","price":372.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967358759197,"sku":"BAA-2961751U","price":255.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967358791965,"sku":"BAA-2961752U","price":271.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967358824733,"sku":"BAA-2961754U","price":401.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967358857501,"sku":"BAA-2961755U","price":415.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Unmounted","offer_id":44967358890269,"sku":"BAA-2961756U","price":488.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Unmounted","offer_id":44967358923037,"sku":"BAA-2961757U","price":1056.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Baader-UBVRI-Filter-Set-Bandpass__47153.1635878681.1280.1280.jpg?v=1684341348"},{"product_id":"baader-photometric-sloan-sdss-ugriz-filter-set","title":"Baader Photometric SLOAN\/SDSS ugriz' Filter Set","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eConforms to the Sloan Digital Sky Survey (SDSS) photometric system\u003c\/li\u003e\n\u003cli\u003eIncludes five filters: u' (ultraviolet), g' (green), r' (red), i' (infrared), and z' (infrared)\u003c\/li\u003e\n\u003cli\u003eEngineered for scientific photometry of variable stars, supernovae, and exoplanets\u003c\/li\u003e\n\u003cli\u003eAvailable in multiple mounted and unmounted sizes for various filter wheels\u003c\/li\u003e\n\u003cli\u003eEnables data collection directly comparable to professional astronomical surveys\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric SLOAN\/SDSS ugriz' Filter Set\u003c\/h2\u003e\n\u003cp\u003eThe Baader Photometric SLOAN\/SDSS ugriz' Filter Set provides the five essential passbands for modern astrophysical research and pro-amateur collaboration. This set is designed for precision photometry, conforming to the Sloan Digital Sky Survey standard for consistent, calibrated measurements of stellar magnitudes and colors. Each filter is manufactured to isolate the specific u', g', r', i', and z' bands, enabling data collection that is directly comparable to professional survey results.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe SLOAN\/SDSS System: A Modern Standard for Astrophysics\u003c\/h3\u003e\n\u003cp\u003eThe ugriz' system is the photometric standard established by the Sloan Digital Sky Survey, one of the most ambitious astronomical surveys ever conducted. Unlike traditional color imaging, photometric filters are designed to have extremely precise, repeatable bandpasses. This allows astronomers anywhere in the world to measure the brightness of an object through each filter and contribute to a global, scientifically valid dataset.\u003c\/p\u003e\n\u003cp\u003eUsing the Baader SLOAN\/SDSS set ensures your measurements adhere to this critical standard. The five filters cover the spectrum from the near-ultraviolet (u') to the near-infrared (z'), providing the data needed to determine stellar temperatures, classify celestial objects, and calculate redshifts of distant galaxies.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eResearch-Grade Data for Pro-Am Collaborations\u003c\/h3\u003e\n\u003cp\u003eThis filter set is engineered for serious scientific application, not just aesthetic imaging. It is the primary tool for contributing to programs run by organizations like the American Association of Variable Star Observers (AAVSO). The precision of the Baader SLOAN filters allows amateur astronomers to produce data with the accuracy required for professional publication.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eExoplanet Transits:\u003c\/strong\u003e Measure the subtle dimming of a star as a planet passes in front of it, contributing to the discovery and characterization of new worlds.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVariable Star Monitoring:\u003c\/strong\u003e Create long-term light curves of pulsating, cataclysmic, or eclipsing variable stars to understand the physical processes driving their behavior.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSupernova Patrols:\u003c\/strong\u003e Detect and measure the changing brightness of exploding stars in other galaxies, providing crucial data for cosmological models.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eSLOAN\/SDSS vs. Johnson-Cousins: Why ugriz' is the New Baseline\u003c\/h3\u003e\n\u003cp\u003eFor decades, the Johnson-Cousins UBVRI system was the dominant photometric standard. While still in use, the SLOAN\/SDSS system offers distinct advantages that have made it the modern successor for CCD-based photometry.\u003c\/p\u003e\n\u003cp\u003eThe key difference lies in the bandpasses. The SLOAN filters are generally broader and have less overlap, which increases signal for faint objects and better matches the spectral response of modern silicon-based CCD and CMOS sensors. The classic Johnson U-band, in particular, is notoriously difficult to work with due to low sensor sensitivity and atmospheric extinction, a problem the SLOAN u' filter mitigates significantly. For any new photometric program, starting with the SLOAN\/SDSS system ensures your results are aligned with current and future professional research.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the main difference between the Baader SLOAN\/SDSS set and a standard LRGB filter set?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003e\u003cstrong\u003eLRGB filters\u003c\/strong\u003e are designed for creating beautiful, full-color astrophotographs. Their bandpasses are broad and often overlap to produce a natural-looking final image. \u003cstrong\u003eThe Baader SLOAN\/SDSS ugriz' set\u003c\/strong\u003e is a scientific tool for \u003cstrong\u003ephotometry\u003c\/strong\u003e. Its bandpasses are precisely defined to match an international standard, allowing you to measure the exact brightness of an object in specific parts of the spectrum. You use LRGB for aesthetics and SLOAN\/SDSS for data.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader ugriz' filters for visual observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, these filters are not intended for visual use. They are designed to pass specific, often narrow, bands of light for measurement by a digital sensor (CCD or CMOS). Visually, they would produce very dim, oddly colored, and uninteresting views. Their purpose is purely for scientific data collection.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the Baader SLOAN set help measure the light curve of an exoplanet transit in front of a star like HD 189733b?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eTo measure an exoplanet transit, you would typically use the Baader SLOAN r' or i' filter, where both the star and your camera sensor are most sensitive. By taking a series of timed exposures before, during, and after the transit of a planet like HD 189733b, you can precisely measure the drop in the star's brightness. The standardized passband of the filter ensures your measurements are consistent and can be compared with data from other observers to confirm the transit's depth and duration.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eMy observatory is in a light-polluted area. Is the Baader SLOAN\/SDSS set effective for photometry from a city?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, photometric filters can be surprisingly effective in light-polluted skies. Because you are measuring a target star relative to nearby, non-variable comparison stars in the same field of view, the background skyglow can be subtracted during data reduction. While pristine dark skies are always better, the precise bandpasses of the Baader SLOAN filters help isolate the starlight from common sources of light pollution, enabling meaningful scientific work even from suburban locations.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy are there five filters in the Baader ugriz' set? Do I need all of them?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe five filters (u', g', r', i', z') measure an object's brightness across the spectrum. The difference in brightness between filters (e.g., g' minus r') gives you the object's \"color index,\" which relates to its temperature. For many projects, like exoplanet transits, you may only use one filter (often r' or i'). For classifying unknown variable stars or studying asteroids, you would need data from multiple filters to determine their physical properties.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDo I need a monochrome or color camera to use the Baader SLOAN\/SDSS filter set?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYou absolutely need a \u003cstrong\u003emonochrome\u003c\/strong\u003e camera for any form of serious photometry. A color camera has its own fixed Bayer matrix (RGB filters) permanently bonded to the sensor, which would interfere with the precise bandpasses of the Baader SLOAN filters. Photometry requires a monochrome sensor and a filter wheel to measure the light from one filter at a time.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter System\u003c\/td\u003e\n\u003ctd\u003eSLOAN\/SDSS (ugriz') Photometric Standard\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" Mounted, 2\" Mounted, 31mm Unmounted, 36mm Unmounted, 50mm Unmounted, 50x50mm Square, 65x65mm Square, 100x100mm Square\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.04 (1.25\" Round Mounted)\u003cbr\u003e0.07 (2\" Round Mounted)\u003cbr\u003e0.02 (36mm Round Unmounted)\u003cbr\u003e0.09 (50mm Round Unmounted)\u003cbr\u003e0.11 (50x50mm Square Filter)\u003cbr\u003e0.19 (65x65mm Square Filter)\u003cbr\u003e0.47 (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Filter)\u003cbr\u003e65 x 65 mm (65x65mm Square Filter)\u003cbr\u003e100 x 100 mm (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eFilter-Set\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eSLOAN, CMOS, CCD\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType of Filter\u003c\/td\u003e\n\u003ctd\u003eBandpass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eSLOAN-ugriz'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to SLOAN-Specification\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967920468253,"sku":"BAA-2961700","price":1158.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967920501021,"sku":"BAA-2961703","price":2002.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967920533789,"sku":"BAA-2961701","price":1385.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967920566557,"sku":"BAA-2961702","price":1529.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967920599325,"sku":"BAA-2961704","price":2403.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Filter","offer_id":44967920632093,"sku":"BAA-2961705","price":2694.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Filter","offer_id":44967920664861,"sku":"BAA-2961706","price":3487.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Filter","offer_id":44967920697629,"sku":"BAA-2961707","price":5751.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Baader-SLOAN-SDSS-ugriz-Filter-Set__24710.1635877668.1280.1280.jpg?v=1684347046"},{"product_id":"baader-photometric-ubvri-b-individual-filter","title":"Baader Photometric UBVRI-B Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eConforms to the standardized Johnson-Cousins\/Bessel B-band passband\u003c\/li\u003e\n\u003cli\u003eDesigned for research-grade scientific photometry\u003c\/li\u003e\n\u003cli\u003eAdvanced anti-reflection and dielectric coatings for maximum transmission\u003c\/li\u003e\n\u003cli\u003ePrecision plano-parallel substrate prevents image degradation\u003c\/li\u003e\n\u003cli\u003eAvailable in 8 formats from 1.25\" mounted to 100x100mm unmounted\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric UBVRI-B Individual Filter\u003c\/h2\u003e\n\u003cp\u003eAvailable in 8 formats from 1.25\" mounted to 100x100mm unmounted, the Baader Photometric UBVRI-B Individual Filter is a scientific instrument that precisely isolates the standardized blue (B) band of the Johnson-Cousins\/Bessel system for research-grade data acquisition. This is not an aesthetic filter for color imaging; it is a tool for collecting accurate stellar magnitude data that can be transformed and compared with results from professional observatories worldwide.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe Bessel B-Band Standard for Scientific Photometry\u003c\/h3\u003e\n\u003cp\u003eThe core function of this filter is to adhere strictly to the Bessel B-band transmission curve. This standardization is critical for scientific applications like monitoring variable stars for the AAVSO, measuring exoplanet transits, or tracking supernova light curves. By ensuring a consistent passband, your instrumental magnitudes become scientifically valid and directly comparable to a global body of research.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eBaader Optical Quality: Precision Manufacturing for Reliable Data\u003c\/h3\u003e\n\u003cp\u003eAccurate photometry demands more than just a specific transmission curve. Baader manufactures these filters with non-compromising optical and mechanical quality to ensure your data is not corrupted by the instrument itself. The optically polished, plano-parallel substrate guarantees that the filter will not introduce aberrations or distort the star's point spread function, which is critical for precise magnitude extraction from your images.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eAdvanced Coatings:\u003c\/strong\u003e Multi-layer dielectric coatings produce a hard, scratch-resistant surface with sharp bandpass cutoffs and high transmission, while anti-reflection coatings minimize halos and internal reflections.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSubstrate Homogeneity:\u003c\/strong\u003e Each filter is made from a carefully selected glass substrate, free of internal stresses and imperfections, ensuring uniform performance across the entire field.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003ePhotometric B-Filter vs. RGB-B Filter: Data vs. Aesthetics\u003c\/h3\u003e\n\u003cp\u003eIt's crucial to understand the distinction between a photometric filter and a standard astrophotography RGB filter. An RGB blue filter is designed to produce pleasing, natural colors in combination with red and green filters. Its passband may be wider or shaped differently to achieve better color balance or block light pollution.\u003c\/p\u003e\n\u003cp\u003eThe Baader Photometric B-Filter has a singular purpose: to replicate the Bessel B-band. Its transmission profile is not optimized for color aesthetics but for scientific accuracy. Choosing this filter means prioritizing data integrity over visual appeal, a trade-off that is essential for any serious photometric research.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the main difference between the Baader Photometric B-filter and a standard RGB blue filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA \u003cstrong\u003estandard RGB blue filter\u003c\/strong\u003e is designed for aesthetic tricolor imaging, with a passband shaped to create good color balance with other filters. The \u003cstrong\u003eBaader Photometric B-filter\u003c\/strong\u003e is a scientific instrument with a passband that strictly adheres to the standardized Johnson-Cousins\/Bessel system, ensuring measurements are comparable to professional data.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader Photometric B-filter for visual observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this filter is not intended for visual use. It is designed for CCD and CMOS cameras and has a relatively narrow, specific passband that would result in a very dim and strongly colored image visually. Its purpose is measurement, not direct observation.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDo I need the other U, V, R, and I filters to do useful science with the Baader B-filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNot necessarily. While a full UBVRI set allows for comprehensive analysis of a star's color and temperature, a significant amount of valuable research is done using a single band. Time-series photometry, such as monitoring a known variable star or an exoplanet transit, can be effectively performed using only the B-filter.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Baader Photometric B-filter to measure the light curve of an exoplanet transit?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYou would mount the Baader Photometric B-filter in your filter wheel and take a continuous series of images of the target star system before, during, and after the predicted transit time. Using photometry software, you measure the brightness of the host star relative to several nearby, non-variable comparison stars in each frame. Plotting this relative brightness over time reveals the characteristic dip in the light curve as the planet passes in front of its star.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy are there so many sizes of the Baader Photometric B-filter available?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe wide range of sizes, from \u003cstrong\u003e1.25\" mounted\u003c\/strong\u003e to \u003cstrong\u003e100x100mm unmounted\u003c\/strong\u003e, ensures compatibility with nearly any imaging setup. Smaller mounted filters are used in standard amateur filter wheels, while larger unmounted filters are required for cameras with large format sensors found in advanced amateur and professional observatory systems.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI want to contribute to the AAVSO database for a Cepheid variable like Delta Cephei. Is this Baader B-filter the right tool?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, this is precisely the correct tool for that task. The American Association of Variable Star Observers (AAVSO) requires data to be submitted in, or be transformable to, the standard UBVRI system. Using a filter like the Baader Photometric B-filter, which is designed to conform to the Bessel B-band, is the critical first step in collecting high-quality, standardized data that can be accepted into their international database.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Unmounted)\u003cbr\u003e0.03 (65x65mm Square Unmounted)\u003cbr\u003e0.08 (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e31 mm (31mm Round Unmounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Unmounted)\u003cbr\u003e65 x 65 mm (65x65mm Square Unmounted)\u003cbr\u003e100 x 100 mm (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eCMOS, CCD, UBVRI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType of Filter\u003c\/td\u003e\n\u003ctd\u003eBandpass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eUBVRI-B\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to Bessel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Photometric UBVRI-B Filter (Selected Size)\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967920927005,"sku":"BAA-2961750B","price":204.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967920959773,"sku":"BAA-2961753B","price":287.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967920992541,"sku":"BAA-2961751B","price":219.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967921025309,"sku":"BAA-2961752B","price":249.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967921058077,"sku":"BAA-2961754B","price":316.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967921090845,"sku":"BAA-2961755B","price":350.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Unmounted","offer_id":44967921123613,"sku":"BAA-2961756B","price":424.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Unmounted","offer_id":44967921156381,"sku":"BAA-2961757B","price":982.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Baader-UBVRI-Filter-Set-Bandpass__47153.1635878681.1280.1280__63433.1635878920.1280.1280.jpg?v=1684347048"},{"product_id":"baader-photometric-ubvri-v-individual-filter","title":"Baader Photometric UBVRI-V Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eBessel V-Band Standard:\u003c\/strong\u003e Precisely conforms to the internationally recognized Johnson-Cousins-Bessel V-band for consistent, scientific-grade magnitude measurements.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePhotometric Grade Optics:\u003c\/strong\u003e Features a plane-parallel substrate with anti-reflection coatings to ensure maximum transmission and prevent ghosting, critical for accurate data collection.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHomofocal (Parfocal) Design:\u003c\/strong\u003e Engineered to be parfocal with other Baader UBVRI filters, eliminating the need to refocus when switching between filters in an automated sequence.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMultiple Formats Available:\u003c\/strong\u003e Offered in 8 formats including standard 1.25\" and 2\" mounted cells and various unmounted sizes up to 100x100mm for nearly any filter wheel or slider.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSealed Coating Edges:\u003c\/strong\u003e The coating edges are sealed, preventing moisture intrusion and degradation over the life of the filter, ensuring long-term stability of the bandpass.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric UBVRI-V Individual Filter\u003c\/h2\u003e\n\u003cp\u003eAvailable in 8 distinct formats from 1.25\" mounted to 100x100mm unmounted, the Baader Photometric UBVRI-V Individual Filter is a scientific instrument designed for the precise measurement of stellar magnitudes. This filter is not a simple colored glass; it is an engineered component that strictly adheres to the Johnson-Cousins-Bessel V-band standard, making it an essential tool for variable star observation, exoplanet transit timing, and stellar classification.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe Johnson-Cousins-Bessel V-Band for Scientific Measurement\u003c\/h3\u003e\n\u003cp\u003eThe Baader V-Filter isolates the \"Visual\" portion of the spectrum, centered around 550nm, to replicate the passband used by professional observatories worldwide. This standardization is the foundation of photometry, allowing your measurements to be directly compared with scientific databases and observations from other astronomers.\u003c\/p\u003e\n\u003cp\u003eUsing this filter, you can create precise light curves of variable stars, measure the dimming of a star during an exoplanet transit, or determine the color index (B-V) of stars to classify their temperature and spectral type. It transforms your imaging setup from a picture-taking device into a scientific measurement tool.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eHomofocal Design for UBVRI Filter Sets\u003c\/h3\u003e\n\u003cp\u003eBaader's photometric filters are designed to be homofocal, or parfocal. This means that when you switch between the V-filter and other Baader UBVRI filters in the same set, your telescope's focus point does not shift. Each filter is manufactured on a substrate of identical thickness, maintaining optical precision across the set.\u003c\/p\u003e\n\u003cp\u003eThis is a critical feature for automated imaging sequences. It eliminates the need for time-consuming refocusing routines between each exposure, maximizing your data collection time on target and preventing focus drift from corrupting a photometric series.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eV-Band vs. Luminance Filters: The Standard for Repeatable Data\u003c\/h3\u003e\n\u003cp\u003eWhile a standard Luminance (L) filter provides a brighter image for general deep-sky astrophotography, it is unsuitable for scientific photometry. L-filters have a very broad, often undefined bandpass that varies between manufacturers and can include significant near-IR transmission, contaminating the visual data.\u003c\/p\u003e\n\u003cp\u003eThe Baader V-Filter's advantage is its precisely defined, repeatable bandpass. A V-magnitude measured with this filter is an objective data point that adheres to an international standard. For any scientific application where data must be consistent and comparable, the V-filter is the correct choice over a generic L-filter.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the primary use for the Baader Photometric V-Filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Baader V-Filter is designed for \u003cstrong\u003escientific photometry\u003c\/strong\u003e. Its main purpose is to accurately measure the brightness of celestial objects, such as variable stars, supernovae, and exoplanet transits, within the standardized Bessel V-band passband.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader V-Filter for imaging galaxies or nebulae?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile you can, it's not the ideal choice. A standard \u003cstrong\u003eLuminance (L) filter\u003c\/strong\u003e has a much broader bandpass and will collect more light, resulting in a brighter, higher signal-to-noise image in less time. The V-filter is a specialized tool for when measurement accuracy is more important than image brightness.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is this V-filter different from a standard green CCD filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA standard green filter is designed for creating RGB color images and its bandpass is not scientifically standardized. The Baader Photometric V-Filter is manufactured to precisely match the \u003cstrong\u003eJohnson-Cousins-Bessel V-band specification\u003c\/strong\u003e, ensuring that measurements taken with it are consistent and comparable to data from professional observatories.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDo I need to refocus when switching between this V-filter and my Baader B and R filters?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. Baader photometric filters are designed to be \u003cstrong\u003ehomofocal (parfocal)\u003c\/strong\u003e. This means you can switch between any of the Baader UBVRI filters in your filter wheel without needing to adjust your focuser, which is essential for automated data acquisition.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Baader V-Filter to measure the light curve of an exoplanet transit like HD 189733b?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eFor an exoplanet transit, you would take a continuous series of exposures of the host star (HD 189733) using the Baader V-Filter before, during, and after the predicted transit time. By measuring the star's brightness in each frame relative to nearby, non-variable comparison stars, you can plot a precise light curve showing the characteristic dip in brightness as the planet passes in front of it.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIf I'm observing a variable star like Algol (Beta Persei) with an 8\" SCT, is the V-filter the right choice?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, absolutely. The V-filter is the standard filter for monitoring the brightness changes of eclipsing binaries like \u003cstrong\u003eAlgol (Beta Persei)\u003c\/strong\u003e. An 8\" SCT provides more than enough light-gathering power, and using the V-filter ensures your magnitude estimates can be submitted to and compared with data from organizations like the AAVSO (American Association of Variable Star Observers).\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric Johnson-Cousins-Bessel V-Band\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes \u0026amp; Formats\u003c\/td\u003e\n\u003ctd\u003e1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Unmounted)\u003cbr\u003e0.03 (65x65mm Square Unmounted)\u003cbr\u003e0.08 (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e31 mm (31mm Round Unmounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Unmounted)\u003cbr\u003e65 x 65 mm (65x65mm Square Unmounted)\u003cbr\u003e100 x 100 mm (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eCMOS, CCD, UBVRI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eUBVRI-V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to Bessel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Baader_Planetarium_Filter_Problems_FAQ_Manual.pdf\" target=\"_blank\"\u003e\u003csvg class=\"DAV-img-box\" viewbox=\"0 0 512 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"\u003e\u003cpath d=\"M0 64C0 28.7 28.7 0 64 0L224 0l0 128c0 17.7 14.3 32 32 32l128 0 0 144-208 0c-35.3 0-64 28.7-64 64l0 144-48 0c-35.3 0-64-28.7-64-64L0 64zm384 64l-128 0L256 0 384 128zM176 352l32 0c30.9 0 56 25.1 56 56s-25.1 56-56 56l-16 0 0 32c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-48 0-80c0-8.8 7.2-16 16-16zm32 80c13.3 0 24-10.7 24-24s-10.7-24-24-24l-16 0 0 48 16 0zm96-80l32 0c26.5 0 48 21.5 48 48l0 64c0 26.5-21.5 48-48 48l-32 0c-8.8 0-16-7.2-16-16l0-128c0-8.8 7.2-16 16-16zm32 128c8.8 0 16-7.2 16-16l0-64c0-8.8-7.2-16-16-16l-16 0 0 96 16 0zm80-112c0-8.8 7.2-16 16-16l48 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 32 32 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 48c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-64 0-64z\" fill=\"#0047a7\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Planetarium Filter Problems FAQ Manual\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967921615133,"sku":"BAA-2961750V","price":206.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967921647901,"sku":"BAA-2961753V","price":290.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967921680669,"sku":"BAA-2961751V","price":220.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967921713437,"sku":"BAA-2961752V","price":251.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967921746205,"sku":"BAA-2961754V","price":319.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967921778973,"sku":"BAA-2961755V","price":351.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Unmounted","offer_id":44967921811741,"sku":"BAA-2961756V","price":427.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Unmounted","offer_id":44967921844509,"sku":"BAA-2961757V","price":979.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/1635878988.1280.1280.jpg?v=1684347050"},{"product_id":"baader-photometric-ubvri-r-individual-filter","title":"Baader Photometric UBVRI-R Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eConforms to the Johnson-Cousins-Bessel R-Band Photometric Standard\u003c\/li\u003e\n\u003cli\u003eEngineered for Scientific Photometry and Data Collection\u003c\/li\u003e\n\u003cli\u003ePlane-Parallel Substrate for Sharp Stars Across the Field\u003c\/li\u003e\n\u003cli\u003eAvailable in 8 Formats for Any Telescope System\u003c\/li\u003e\n\u003cli\u003eOffered in Mounted (1.25\", 2\") and Unmounted (31mm, 36mm, 50mm, 50x50mm, 65x65mm, 100x100mm) versions\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric UBVRI-R Individual Filter\u003c\/h2\u003e\n\u003cp\u003eThe Baader Photometric UBVRI-R Individual Filter provides a standardized red passband for scientific photometry, available in 8 distinct formats from 1.25\" round mounted to 100x100mm square unmounted to precisely replicate the Johnson-Cousins-Bessel 'R' band. This ensures your measurements are comparable with professional datasets worldwide, with options including 1.25\" and 2\" mounted versions, and 31mm, 36mm, and 50mm round or 50x50mm, 65x65mm, and 100x100mm square unmounted formats for maximum system compatibility.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe Bessel R-Band Standard: 1 Filter for Consistent Data\u003c\/h3\u003e\n\u003cp\u003eThis filter is not designed for aesthetic imaging; it is a scientific instrument. Its transmission profile is engineered to match the Johnson-Cousins-Bessel R-band, the global standard for astronomical photometry. This adherence means the brightness measurements you take of variable stars, exoplanet transits, or supernovae are directly comparable to data from other observatories, forming a crucial part of collaborative pro-am research.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003ePlane-Parallel Substrate: 0 Internal Reflections for Accurate Photometry\u003c\/h3\u003e\n\u003cp\u003eIn photometry, any artifact can corrupt the data. Baader manufactures these filters from fine-optically polished, plane-parallel glass to eliminate halos or ghost images that could alter stellar magnitude measurements. The goal is 0 internal reflections affecting the focal plane, ensuring that the light measured is purely from the target star. Advanced, non-ageing coatings and blackened filter edges further suppress stray light for the highest possible contrast and data accuracy.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003e8 Formats for Universal Integration: From 1.25\" to 100x100mm\u003c\/h3\u003e\n\u003cp\u003eBaader produces this photometric filter in 8 formats to accommodate nearly any imaging system. Whether you use a standard 1.25\" filter wheel on a small refractor or a large format camera on a research-grade reflector, there is a size that fits your optical train.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" and 2\" Mounted:\u003c\/strong\u003e Ready to thread into standard filter wheels and accessories for immediate use.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e31mm and 36mm Unmounted:\u003c\/strong\u003e Common sizes for dedicated astronomy filter wheels, offering a larger clear aperture than their 1.25\" counterparts.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e50mm Round, 50x50mm, 65x65mm, and 100x100mm Square:\u003c\/strong\u003e Unmounted formats for large-format CCDs and professional filter sliders, ensuring the sensor is fully illuminated without vignetting.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eBaader Photometric R vs. LRGB Red: 1 Standard for Science\u003c\/h3\u003e\n\u003cp\u003eA standard LRGB red filter is designed to gather maximum signal for creating visually pleasing images, often with a broad passband and gentle cutoffs. A photometric filter has a different priority: strict adherence to 1 scientific standard. The Baader Photometric R filter features the sharp, precise bandpass required by the Bessel system. This may result in slightly lower overall light transmission compared to a deep-sky filter, which is the necessary trade-off for producing scientifically valid, repeatable, and comparable data.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy do I need a Baader Photometric R filter instead of my regular LRGB red filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYour LRGB red filter is designed for beautiful astrophotos by capturing a broad swath of red light. The \u003cstrong\u003eBaader Photometric R filter\u003c\/strong\u003e is a scientific tool designed to isolate a very specific, standardized slice of the red spectrum defined by the Johnson-Cousins-Bessel system. This precision allows you to take brightness measurements (photometry) that can be compared with data from other astronomers and professional observatories worldwide.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat kind of data can I collect on a variable star like Algol (Beta Persei) with the Baader Photometric R filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eUsing the \u003cstrong\u003eBaader Photometric R filter\u003c\/strong\u003e, you can create a light curve for Algol. By taking a series of timed exposures, you can precisely measure its change in magnitude as its companion star eclipses it. Because the filter conforms to the R-band standard, your data can be submitted to organizations like the AAVSO (American Association of Variable Star Observers) and contribute to the long-term scientific study of the star.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Baader Photometric R filter parfocal with other Baader filters?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eBaader Planetarium engineers their filter sets to be as close to parfocal as possible, meaning minimal refocusing is needed when switching between them. However, for precise scientific work like photometry, it is always best practice to briefly check and adjust focus after changing any filter, including the \u003cstrong\u003eBaader Photometric R filter\u003c\/strong\u003e, to ensure the sharpest possible data.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhich size of the Baader Photometric R filter do I need for my 8\" SCT with a standard filter wheel?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eFor an 8\" SCT using a common 1.25\" filter wheel (like those from ZWO or QHY), the \u003cstrong\u003e1.25\" Round Mounted Baader Photometric R filter\u003c\/strong\u003e is the correct choice. If you are using a larger 2\" filter wheel or an off-axis guider that requires more back focus, the 2\" mounted version would be appropriate. For unmounted filter wheels, check your carousel's documentation for the correct diameter (e.g., 31mm or 36mm).\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader Photometric R filter for visual observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile you can look through the \u003cstrong\u003eBaader Photometric R filter\u003c\/strong\u003e, it is not designed for visual use. Its narrow, specific bandpass is optimized for digital sensors (CCDs and CMOS cameras). For visual observation, a standard red planetary or deep-sky filter will provide a brighter and more useful view.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I clean my Baader Photometric R filter without damaging the coatings?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eUse a gentle, multi-step process. First, use a blower bulb to remove loose dust. If smudges remain, apply a small amount of pure, lab-grade isopropyl alcohol or a dedicated optical cleaning solution to a clean microfiber cloth or optical wipe. Gently wipe the surface in a circular motion from the center outwards. Never apply fluid directly to the filter surface.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Options\u003c\/td\u003e\n\u003ctd\u003e1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Unmounted)\u003cbr\u003e0.03 (65x65mm Square Unmounted)\u003cbr\u003e0.08 (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e31 mm (31mm Round Unmounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Unmounted)\u003cbr\u003e65 x 65 mm (65x65mm Square Unmounted)\u003cbr\u003e100 x 100 mm (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eCMOS, CCD, UBVRI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType of Filter\u003c\/td\u003e\n\u003ctd\u003eBandpass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eUBVRI-R\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to Bessel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Photometric UBVRI-R Individual Filter\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Baader_Planetarium_Cleaning_and_Maintenance_of_Optics_Manual.pdf\" target=\"_blank\"\u003e\u003csvg class=\"DAV-img-box\" viewbox=\"0 0 512 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"\u003e\u003cpath d=\"M0 64C0 28.7 28.7 0 64 0L224 0l0 128c0 17.7 14.3 32 32 32l128 0 0 144-208 0c-35.3 0-64 28.7-64 64l0 144-48 0c-35.3 0-64-28.7-64-64L0 64zm384 64l-128 0L256 0 384 128zM176 352l32 0c30.9 0 56 25.1 56 56s-25.1 56-56 56l-16 0 0 32c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-48 0-80c0-8.8 7.2-16 16-16zm32 80c13.3 0 24-10.7 24-24s-10.7-24-24-24l-16 0 0 48 16 0zm96-80l32 0c26.5 0 48 21.5 48 48l0 64c0 26.5-21.5 48-48 48l-32 0c-8.8 0-16-7.2-16-16l0-128c0-8.8 7.2-16 16-16zm32 128c8.8 0 16-7.2 16-16l0-64c0-8.8-7.2-16-16-16l-16 0 0 96 16 0zm80-112c0-8.8 7.2-16 16-16l48 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 32 32 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 48c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-64 0-64z\" fill=\"#0047a7\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Planetarium Cleaning and Maintenance of Optics Manual\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty Policy\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967922041117,"sku":"BAA-2961750R","price":203.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967922073885,"sku":"BAA-2961753R","price":283.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967922106653,"sku":"BAA-2961751R","price":222.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967922139421,"sku":"BAA-2961752R","price":252.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967922172189,"sku":"BAA-2961754R","price":314.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967922204957,"sku":"BAA-2961755R","price":348.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Unmounted","offer_id":44967922237725,"sku":"BAA-2961756R","price":414.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Unmounted","offer_id":44967922270493,"sku":"BAA-2961757R","price":983.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/1635878988.1280.1280__49917.1635879064.1280.1280.jpg?v=1684347056"},{"product_id":"baader-photometric-ubvri-i-individual-filter","title":"Baader Photometric UBVRI-I Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eConforms to the Johnson-Cousins UBVRI Photometric System\u003c\/li\u003e\n\u003cli\u003eOptimized for the Bessel I-Band (Infrared)\u003c\/li\u003e\n\u003cli\u003eHomofocal Design for Parfocal Operation with other Baader UBVRI filters\u003c\/li\u003e\n\u003cli\u003eAdvanced Anti-Reflection and Dielectric Coatings\u003c\/li\u003e\n\u003cli\u003eAvailable in 8 formats, including 1.25\" and 2\" mounted sizes\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric UBVRI-I Individual Filter\u003c\/h2\u003e\n\u003cp\u003eThe Baader Photometric UBVRI-I Filter is an essential tool for scientific astronomical measurement, designed to precisely isolate the infrared I-band as defined by the Johnson-Cousins UBVRI system. Engineered for data acquisition rather than visual appeal, this filter provides the strict, repeatable bandpass required for variable star observation, exoplanet transit timing, and stellar classification. Each filter is manufactured to be homofocal with its U, B, V, and R counterparts, ensuring your optical system remains parfocal when switching between filters during a photometric sequence.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe Bessel I-Band Standard for Scientific Photometry\u003c\/h3\u003e\n\u003cp\u003eThis filter is not a generic infrared-pass filter; it is a scientific instrument designed to conform to the specific transmission curve of the Bessel I-band. This adherence to an established standard allows your measurements to be directly comparable to data from professional observatories and scientific literature worldwide. The result is verifiable, publishable data for your research projects.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eHomofocal Engineering for Parfocal Operation\u003c\/h3\u003e\n\u003cp\u003eFor photometric sequences that require cycling through multiple filters, maintaining focus is critical. Baader engineers their UBVRI filters to be homofocal, meaning each filter has an identical substrate thickness and optical effect. This ensures that once you achieve focus with one filter in the set, all others will snap to the same focal point, eliminating the need to refocus and saving critical time during observation.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlaneoptically Polished Substrate:\u003c\/strong\u003e Each filter is polished to a high degree of flatness to prevent any degradation of the incoming wavefront, preserving the sharpness of your telescope's optics.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAdvanced Anti-Reflection Coatings:\u003c\/strong\u003e Multi-layer coatings eliminate ghosting and internal reflections, maximizing signal-to-noise ratio by ensuring that light from your target reaches the sensor without interference.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eMulti-Format Availability: 8 Options from 1.25\" to 100x100mm\u003c\/h3\u003e\n\u003cp\u003eThe Baader Photometric I-Filter is available in a comprehensive range of 8 sizes to integrate into any imaging train. Whether you are using a small guide camera for transit timings or a large-format CCD on a research-grade instrument, there is a format to match your equipment. Options include standard 1.25\" and 2\" round mounted filters for common filter wheels, as well as unmounted round and square filters up to 100x100mm for professional camera systems.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003ePhotometric vs. Imaging Filters: Measurement over Aesthetics\u003c\/h3\u003e\n\u003cp\u003eIt is important to understand the distinction between a photometric filter and a standard LRGB or narrowband imaging filter. While an imaging filter is designed to produce visually pleasing color images, a photometric filter is built for metrology.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eStrict Bandpass:\u003c\/strong\u003e The Baader Photometric I-Filter has a very sharp cutoff and a flat-topped transmission curve that adheres strictly to the Bessel I-band definition. This prioritizes measurement accuracy over capturing faint, out-of-band signal.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNo IR\/UV Cut:\u003c\/strong\u003e Unlike LRGB filters, this filter does not include additional blocking. It is designed to be used with sensors that have a known spectral response, as is standard practice in photometry.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the primary use for the Baader Photometric I-Filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Baader Photometric I-Filter is designed for \u003cstrong\u003escientific photometry\u003c\/strong\u003e. Its primary application is measuring the brightness of celestial objects in the infrared portion of the spectrum, as defined by the Johnson-Cousins UBVRI system. This is crucial for studying variable stars, monitoring supernova light curves, and analyzing the characteristics of stars and galaxies.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs this Baader I-band filter the same as a standard near-IR imaging filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, they are fundamentally different. A standard near-IR filter has a broad, less-defined passband designed to capture as much signal as possible for imaging. The Baader Photometric I-Filter has a precisely defined, rectangular transmission profile that conforms to the scientific Bessel I-band standard, prioritizing measurement accuracy and repeatability over raw signal.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Baader I-Filter to measure a variable star like Mira (Omicron Ceti)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eMira is a long-period variable star whose brightness changes significantly, especially in the infrared. To measure its magnitude with the Baader I-Filter, you would take a series of exposures of Mira, along with several nearby, non-variable \"comparison\" stars of known I-band magnitude. Using photometry software, you would measure the instrumental magnitude of all stars and use the known magnitudes of the comparison stars to calibrate your measurement of Mira, producing a standardized I-band magnitude for your observation time.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is the homofocal design of the Baader Photometric I-Filter important?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe homofocal design means all Baader UBVRI filters have the same optical thickness, making them \u003cstrong\u003eparfocal\u003c\/strong\u003e. When you are taking photometric measurements, you often need to cycle through U, B, V, R, and I filters quickly. A parfocal set means you only have to focus once. When you switch filters, the image remains sharp, which is critical for automated data acquisition and maintaining consistency across your dataset.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDo I need the entire UBVRI set to use the Baader I-Filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, you can use the Baader I-Filter on its own for projects specifically requiring I-band data. However, its true power is realized as part of the complete UBVRI set, which allows you to determine the color indices (like V-I) of stars. These color indices are essential for determining a star's temperature, spectral type, and other physical properties.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhich Baader filter format is best for my SBIG STX-16803 camera on a PlaneWave CDK?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eFor a large-format camera like the SBIG STX-16803, which often uses a 7-position or 8-position filter wheel, you would typically use one of the larger unmounted square formats. The \u003cstrong\u003e50x50mm Square Unmounted\u003c\/strong\u003e option is a common standard for this class of instrument, as it is large enough to prevent vignetting on the large KAF-16803 sensor, even with a fast optical system like a PlaneWave CDK.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric Bessel I-Band\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSystem\u003c\/td\u003e\n\u003ctd\u003eJohnson-Cousins UBVRI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eParfocal\u003c\/td\u003e\n\u003ctd\u003eYes, homofocal with other Baader UBVRI filters\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eDielectric and Anti-Reflection\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSubstrate\u003c\/td\u003e\n\u003ctd\u003ePlaneoptically Polished Glass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Options\u003c\/td\u003e\n\u003ctd\u003e1.25\" Mounted, 2\" Mounted, 31mm Unmounted, 36mm Unmounted, 50mm Unmounted, 50x50mm Unmounted, 65x65mm Unmounted, 100x100mm Unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Unmounted)\u003cbr\u003e0.03 (65x65mm Square Unmounted)\u003cbr\u003e0.08 (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e31 mm (31mm Round Unmounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Unmounted)\u003cbr\u003e65 x 65 mm (65x65mm Square Unmounted)\u003cbr\u003e100 x 100 mm (100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eCMOS, CCD, UBVRI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eUBVRI-I\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to Bessel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967922401565,"sku":"BAA-2961750I","price":231.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967922434333,"sku":"BAA-2961753I","price":372.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967922467101,"sku":"BAA-2961751I","price":255.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967922499869,"sku":"BAA-2961752I","price":273.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967922532637,"sku":"BAA-2961754I","price":402.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967922565405,"sku":"BAA-2961755I","price":417.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Unmounted","offer_id":44967922598173,"sku":"BAA-2961756I","price":488.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Unmounted","offer_id":44967922630941,"sku":"BAA-2961757I","price":1041.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Baader-UBVRI-Filter-Set-Bandpass__47153.1635878681.1280.1280__29804.1635879159.1280.1280.jpg?v=1684347059"},{"product_id":"baader-photometric-sloan-sdss-u-individual-filter","title":"Baader Photometric SLOAN\/SDSS u' Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eStandardized SLOAN\/SDSS u'-band photometric filter\u003c\/li\u003e\n\u003cli\u003eIsolates the near-ultraviolet (UV) spectrum for scientific analysis\u003c\/li\u003e\n\u003cli\u003eDesigned for repeatable, high-precision stellar magnitude measurements\u003c\/li\u003e\n\u003cli\u003eIdeal for pro-am collaboration, variable star research, and exoplanet transits\u003c\/li\u003e\n\u003cli\u003eAvailable in multiple mounted and unmounted sizes for various filter wheels\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric SLOAN\/SDSS u' Individual Filter\u003c\/h2\u003e\n\u003cp\u003eThe Baader Photometric SLOAN\/SDSS u' Filter is a specialized scientific instrument designed for precise data acquisition in the near-ultraviolet spectrum. This is not a filter for creating color composites; its purpose is to isolate a specific spectral window defined by the Sloan Digital Sky Survey, enabling astronomers to measure the brightness of celestial objects with the high accuracy required for research-grade photometry. It is a critical tool for studying high-energy astronomical phenomena, such as cataclysmic variables, hot young stars, and active galactic nuclei.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe Role of the u'-Band in Photometry\u003c\/h3\u003e\n\u003cp\u003eThe u' (ultraviolet) band is the shortest wavelength filter in the five-filter SLOAN\/SDSS system. It provides a unique window into high-energy astrophysical processes that are faint or invisible at longer wavelengths. By measuring flux in the u'-band, you can characterize the temperature of very hot O- and B-type stars or quantify the violent accretion processes occurring in binary star systems.\u003c\/p\u003e\n\u003cp\u003eThis filter's strict adherence to the SDSS standard ensures your data is comparable to that from professional surveys, making it invaluable for pro-am collaborations. Whether you are contributing to the AAVSO database or conducting independent research, the Baader u' filter provides a standardized, repeatable measurement baseline.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe u' Filter vs. Other SLOAN\/SDSS Bands\u003c\/h3\u003e\n\u003cp\u003eWhile the u' filter is powerful on its own, its true scientific utility is often realized as part of the complete u'g'r'i'z' set. Each filter provides a piece of the puzzle for determining an object's temperature, composition, and distance through color indices.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eu' vs. g' and r':\u003c\/strong\u003e The u'-band is essential for measuring the \"Balmer break\" in stellar spectra, a key indicator of temperature and surface gravity. A u'-g' color index is far more sensitive to temperature variations in hot stars than a g'-r' index alone.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTrade-offs:\u003c\/strong\u003e The trade-off for this specialized scientific capability is its unsuitability for general-purpose imaging. The u'-band image will appear dim, have low contrast, and will not contribute to a natural-color LRGB composite. This filter is exclusively for data collection with a monochrome sensor.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eEngineered for Repeatable Scientific Measurement\u003c\/h3\u003e\n\u003cp\u003eA filter's \"photometric\" designation implies a higher standard of manufacturing. While specific transmission values are not provided, these filters are designed with the core requirements of scientific measurement in mind: steep bandpass slopes to cleanly isolate the desired wavelength, and stable, non-ageing coatings to ensure that measurements taken years apart remain consistent.\u003c\/p\u003e\n\u003cp\u003eBaader's construction aims to minimize halos and internal reflections, preserving the integrity of stellar point-spread functions (PSFs) for accurate magnitude extraction. Available in a wide range of sizes from 1.25\" mounted to 100x100mm unmounted, the Baader u' filter can be integrated into nearly any amateur or institutional imaging train.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the Baader Photometric u' filter primarily used for?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Baader u' filter is a scientific tool used with a monochrome camera for \u003cstrong\u003ephotometry\u003c\/strong\u003e—the precise measurement of an object's brightness. It's specifically used to study objects that are bright in the near-ultraviolet, such as hot young stars, accretion disks around white dwarfs (cataclysmic variables), and distant quasars.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader u' filter for visual observing or color imaging?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this filter is not suitable for either. Visually, the near-UV bandpass will result in an extremely dim, colorless image. For color imaging (LRGB), the u' band does not correspond to a standard color channel and will not produce a natural-looking result. It is designed exclusively for scientific measurement with a monochrome sensor.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Baader u' filter to study a cataclysmic variable like SS Cygni with my SCT?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eSS Cygni is a dwarf nova that undergoes dramatic outbursts. The source of these outbursts is the accretion disk, which becomes extremely hot and bright in the ultraviolet. Using the Baader u' filter on your SCT with a monochrome camera, you can take a series of exposures and measure the changing brightness of SS Cygni relative to nearby, stable stars. This allows you to create a light curve of the outburst in the u'-band, providing critical data on the physics of the accretion process.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDo I need the entire Baader SLOAN\/SDSS filter set for my research?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIt depends on your goal. For monitoring the brightness of an object in a single high-energy band, the \u003cstrong\u003eu' filter alone\u003c\/strong\u003e is sufficient. However, to determine an object's temperature or create a Spectral Energy Distribution (SED), you need to measure its brightness through multiple filters (e.g., u', g', and r') to calculate color indices.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the Baader u' filter work with my observatory's automated filter wheel?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The Baader u' filter is offered in all standard astronomical sizes, including \u003cstrong\u003e1.25\" and 2\" mounted\u003c\/strong\u003e for smaller wheels, and unmounted round (\u003cstrong\u003e31mm, 36mm, 50mm\u003c\/strong\u003e) and square (\u003cstrong\u003e50x50mm, 65x65mm, 100x100mm\u003c\/strong\u003e) formats for larger, research-grade filter carousels. Be sure to select the option that matches your filter wheel's specifications.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat makes this Baader u' filter \"photometric\"?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA \"photometric\" filter is manufactured to meet a strict transmission standard, in this case, the Sloan Digital Sky Survey u' band. This ensures that data you collect is consistent and can be compared directly with data from other observers and professional surveys using the same system. The design emphasizes sharp bandpass cutoffs, high transmission, and coating stability over time.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric SLOAN\/SDSS u' Bandpass Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" Mounted, 2\" Mounted, 31mm Unmounted, 36mm Unmounted, 50mm Unmounted, 50x50mm Square, 65x65mm Square, 100x100mm Square\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Filter)\u003cbr\u003e0.03 (65x65mm Square Filter)\u003cbr\u003e0.08 (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Filter)\u003cbr\u003e65 x 65 mm (65x65mm Square Filter)\u003cbr\u003e100 x 100 mm (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eSLOAN, CMOS, CCD\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eSLOAN-u'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to SLOAN-Specification\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Photometric SLOAN\/SDSS u' Individual Filter (selected size)\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eFilter Case\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Baader_Planetarium_Cleaning_and_Maintenance_of_Optics_Manual.pdf\" target=\"_blank\"\u003e\u003csvg class=\"DAV-img-box\" viewbox=\"0 0 512 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"\u003e\u003cpath d=\"M0 64C0 28.7 28.7 0 64 0L224 0l0 128c0 17.7 14.3 32 32 32l128 0 0 144-208 0c-35.3 0-64 28.7-64 64l0 144-48 0c-35.3 0-64-28.7-64-64L0 64zm384 64l-128 0L256 0 384 128zM176 352l32 0c30.9 0 56 25.1 56 56s-25.1 56-56 56l-16 0 0 32c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-48 0-80c0-8.8 7.2-16 16-16zm32 80c13.3 0 24-10.7 24-24s-10.7-24-24-24l-16 0 0 48 16 0zm96-80l32 0c26.5 0 48 21.5 48 48l0 64c0 26.5-21.5 48-48 48l-32 0c-8.8 0-16-7.2-16-16l0-128c0-8.8 7.2-16 16-16zm32 128c8.8 0 16-7.2 16-16l0-64c0-8.8-7.2-16-16-16l-16 0 0 96 16 0zm80-112c0-8.8 7.2-16 16-16l48 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 32 32 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 48c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-64 0-64z\" fill=\"#0047a7\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Planetarium Cleaning and Maintenance of Optics Manual\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967922729245,"sku":"BAA-2961700U","price":225.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967922762013,"sku":"BAA-2961703U","price":370.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967922794781,"sku":"BAA-2961701U","price":279.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967922827549,"sku":"BAA-2961702U","price":297.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967922860317,"sku":"BAA-2961704U","price":443.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Filter","offer_id":44967922893085,"sku":"BAA-2961705U","price":516.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Filter","offer_id":44967922925853,"sku":"BAA-2961706U","price":632.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Filter","offer_id":44967922958621,"sku":"BAA-2961707U","price":1012.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Baader-SLOAN-SDSS-ugriz-Filter-Set-Bandpass__47175.1635877722.1280.1280__53044.1635880180.1280.1280.jpg?v=1684347062"},{"product_id":"baader-photometric-sloan-sdss-g-individual-filter","title":"Baader Photometric SLOAN\/SDSS g' Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eSLOAN\/SDSS g' Bandpass:\u003c\/strong\u003e Conforms to the modern standard for astronomical photometry.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePhotometric Grade:\u003c\/strong\u003e Produces scientifically valid data for research, including light curves and color indices.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMultiple Sizes:\u003c\/strong\u003e Available in 8 formats for compatibility with all standard filter wheels and sliders.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrecision Manufacturing:\u003c\/strong\u003e Advanced coatings and a fine-optically polished substrate prevent image degradation.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric SLOAN\/SDSS g' Individual Filter\u003c\/h2\u003e\n\u003cp\u003eThe Baader Photometric SLOAN\/SDSS g' Individual Filter enables professional-grade data acquisition by precisely isolating the standardized g' (green) bandpass—available in 8 distinct formats from 1.25\" mounted cells to 100x100mm unmounted squares—allowing astronomers to generate light curves and color indices for variable stars and exoplanets with data directly comparable to major sky surveys.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe SLOAN\/SDSS g' Standard for Scientific Data\u003c\/h3\u003e\n\u003cp\u003eThis filter is not for creating aesthetically pleasing color images; it is a scientific instrument designed for photometry. It strictly adheres to the bandpass defined by the Sloan Digital Sky Survey (SDSS), the most extensive astronomical survey to date. This standardization is critical, as it ensures that measurements you take in your backyard can be accurately compared, transformed, and combined with data from professional observatories worldwide.\u003c\/p\u003e\n\u003cp\u003eBy isolating the g' band, you can accurately measure stellar magnitudes and color indices, which are fundamental for classifying stars, studying stellar evolution, and detecting the subtle dimming caused by an exoplanet transit. For serious amateur astronomers contributing to organizations like the AAVSO or conducting pro-am collaborations, using a standardized filter like this is non-negotiable.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003e8 Filter Sizes for Universal Integration\u003c\/h3\u003e\n\u003cp\u003eBaader offers the SLOAN\/SDSS g' filter in a comprehensive range of sizes to fit virtually any imaging setup. This ensures that whether you are using a small personal telescope or a large observatory-class instrument, you can integrate this photometric filter into your system without compromise.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMounted Options:\u003c\/strong\u003e The \u003cstrong\u003e1.25\"\u003c\/strong\u003e and \u003cstrong\u003e2\"\u003c\/strong\u003e round mounted filters are ready to thread into standard filter wheels and eyepiece barrels.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnmounted Round Options:\u003c\/strong\u003e For custom mounting in modern filter carousels, \u003cstrong\u003e31mm\u003c\/strong\u003e and \u003cstrong\u003e36mm\u003c\/strong\u003e unmounted filters provide a perfect fit.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLarge Format Options:\u003c\/strong\u003e For imagers with large full-frame or medium-format sensors, Baader provides \u003cstrong\u003e50mm\u003c\/strong\u003e round, \u003cstrong\u003e50x50mm\u003c\/strong\u003e, \u003cstrong\u003e65x65mm\u003c\/strong\u003e, and \u003cstrong\u003e100x100mm\u003c\/strong\u003e square filters to prevent vignetting and ensure even illumination across the entire field.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eSLOAN\/SDSS g' vs. Johnson-Cousins V: The Modern Standard\u003c\/h3\u003e\n\u003cp\u003eWhile the Johnson-Cousins UBVRI system was the standard for decades, it was designed for photomultiplier tubes. The SLOAN\/SDSS u'g'r'i'z' system was developed specifically for the response of modern CCD and CMOS sensors. The Baader g' filter offers a squarer, more defined transmission curve than the older Johnson V filter, with minimal overlap with adjacent bands.\u003c\/p\u003e\n\u003cp\u003eThis clean separation between bands is crucial for accurate color-color diagrams and photometric transformations. While the g' band is centered in the green part of the spectrum like the V band, it is not a direct replacement. For modern scientific work, the SLOAN\/SDSS system is the current professional standard, and this filter is your entry point to that system.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the Baader SLOAN\/SDSS g' filter primarily used for?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Baader SLOAN\/SDSS g' filter is a scientific tool for \u003cstrong\u003ephotometry\u003c\/strong\u003e—the precise measurement of the brightness of celestial objects. Its primary uses include creating light curves for variable stars, detecting exoplanet transits, and determining the color index of stars, asteroids, and supernovae.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader SLOAN\/SDSS g' filter for visual observing or LRGB imaging?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this filter is not recommended for general visual use or as a substitute for a standard green (G) filter in an LRGB set. Its specific, narrow bandpass is designed for measurement, not for creating natural-color views or images. Visually, it would produce a strong monochromatic green image, and in LRGB imaging, it would result in an incorrect color balance.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the Baader SLOAN\/SDSS g' filter's bandpass differ from a Johnson V filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe SLOAN g' band is centered in the green region of the spectrum, similar to the Johnson V (Visual) band. However, the g' band is wider and has a \"squarer\" transmission profile designed for modern digital sensors. The two systems are not directly interchangeable, and photometric measurements taken with a g' filter must be transformed mathematically if they are to be compared to older V-band data.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI have a Johnson-Cousins filter set. Should I upgrade to the Baader SLOAN\/SDSS g' filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIf you are conducting scientific photometry and want your data to be compatible with modern professional surveys and databases, upgrading to the SLOAN\/SDSS system is highly recommended. The Johnson-Cousins system is still valid, but the SLOAN system is the current standard for digital detectors and is preferred for most pro-am research projects.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Baader SLOAN\/SDSS g' filter to measure the light curve of an exoplanet transit in Cygnus?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYou would pair the Baader SLOAN\/SDSS g' filter with a monochrome camera on your telescope and take a continuous series of exposures of the target star before, during, and after the predicted transit time. Using photometry software, you would measure the brightness of the target star relative to several nearby, non-variable comparison stars in each frame. The g' filter ensures these measurements are consistent and standardized, allowing you to plot a precise light curve showing the characteristic dip in brightness as the planet passes in front of its star.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIf I'm imaging the Sombrero Galaxy (M104) with a 10\" Newtonian and the Baader SLOAN\/SDSS g' filter, what data do I get?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eImaging M104 with the Baader SLOAN\/SDSS g' filter will produce a high-contrast monochrome image showing the galaxy's structure in the green part of the spectrum. Scientifically, this data represents the galaxy's brightness in the g' band. If you also imaged it with r' and i' filters, you could combine the data to measure the color indices of different regions, helping to distinguish between older, yellower stars in the central bulge and younger, bluer star-forming regions in the disk.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric SLOAN\/SDSS g' Band\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes \u0026amp; Mounts\u003c\/td\u003e\n\u003ctd\u003e1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square, 65x65mm Square, 100x100mm Square\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Filter)\u003cbr\u003e0.03 (65x65mm Square Filter)\u003cbr\u003e0.08 (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Filter)\u003cbr\u003e65 x 65 mm (65x65mm Square Filter)\u003cbr\u003e100 x 100 mm (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eSLOAN, CMOS, CCD\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eSLOAN-g'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to SLOAN-Specification\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Photometric SLOAN\/SDSS g' Individual Filter (in selected size)\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Baader_Planetarium_Filter_Problems_FAQ_Manual.pdf\" target=\"_blank\"\u003e\u003csvg class=\"DAV-img-box\" viewbox=\"0 0 512 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"\u003e\u003cpath d=\"M0 64C0 28.7 28.7 0 64 0L224 0l0 128c0 17.7 14.3 32 32 32l128 0 0 144-208 0c-35.3 0-64 28.7-64 64l0 144-48 0c-35.3 0-64-28.7-64-64L0 64zm384 64l-128 0L256 0 384 128zM176 352l32 0c30.9 0 56 25.1 56 56s-25.1 56-56 56l-16 0 0 32c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-48 0-80c0-8.8 7.2-16 16-16zm32 80c13.3 0 24-10.7 24-24s-10.7-24-24-24l-16 0 0 48 16 0zm96-80l32 0c26.5 0 48 21.5 48 48l0 64c0 26.5-21.5 48-48 48l-32 0c-8.8 0-16-7.2-16-16l0-128c0-8.8 7.2-16 16-16zm32 128c8.8 0 16-7.2 16-16l0-64c0-8.8-7.2-16-16-16l-16 0 0 96 16 0zm80-112c0-8.8 7.2-16 16-16l48 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 32 32 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 48c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-64 0-64z\" fill=\"#0047a7\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Planetarium Filter Problems FAQ Manual\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967923056925,"sku":"BAA-2961700G","price":216.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967923089693,"sku":"BAA-2961703G","price":362.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967923122461,"sku":"BAA-2961701G","price":272.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967923155229,"sku":"BAA-2961702G","price":289.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967923187997,"sku":"BAA-2961704G","price":434.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Filter","offer_id":44967923220765,"sku":"BAA-2961705G","price":507.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Filter","offer_id":44967923253533,"sku":"BAA-2961706G","price":624.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Filter","offer_id":44967923286301,"sku":"BAA-2961707G","price":1005.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/1635880327.1280.1280.jpg?v=1684347066"},{"product_id":"baader-photometric-sloan-sdss-r-individual-filter","title":"Baader Photometric SLOAN\/SDSS r' Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eConforms to the scientific SLOAN\/SDSS r' photometric system\u003c\/li\u003e\n\u003cli\u003eEngineered for professional and amateur astronomical research\u003c\/li\u003e\n\u003cli\u003eAvailable in 8 formats, from 1.25\" mounted to 100x100mm unmounted\u003c\/li\u003e\n\u003cli\u003eFeatures plane-parallel substrates for sharp images free of distortion\u003c\/li\u003e\n\u003cli\u003eNon-aging sealed coating edges ensure stable measurements over years of use\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric SLOAN\/SDSS r' Individual Filter\u003c\/h2\u003e\n\u003cp\u003eThe Baader Photometric SLOAN\/SDSS r' Filter is available in 8 distinct formats, including standard 1.25-inch and 2-inch mounted options for common filter wheels. For larger systems, unmounted versions range from 31mm round to massive 100x100mm square filters, accommodating the largest observatory-grade sensors.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe SLOAN\/SDSS r' Bandpass: A Standard for Scientific Photometry\u003c\/h3\u003e\n\u003cp\u003eThis filter is not for creating conventional color images; its purpose is to isolate a specific portion of the red spectrum defined by the Sloan Digital Sky Survey (SDSS). This adherence to a professional standard allows your measurements to be directly comparable to global astronomical data, transforming your setup into a tool for serious research.\u003c\/p\u003e\n\u003cp\u003eBy using the SLOAN\/SDSS r' filter, you can accurately measure the brightness of variable stars, detect the subtle dimming of exoplanet transits, or contribute to supernova light curve monitoring. It ensures that the data you collect is consistent, repeatable, and scientifically valuable.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eBaader's Optical Quality: Plane-Parallel Substrates for Unwavering Precision\u003c\/h3\u003e\n\u003cp\u003eFor photometric work, the physical quality of the filter is as critical as its transmission curve. Baader manufactures these filters with optically plane-parallel substrates, guaranteeing that they will not introduce astigmatism or other aberrations into your light path. This maintains the sharpness of your star images, which is essential for accurate magnitude measurements.\u003c\/p\u003e\n\u003cp\u003eFurthermore, each filter features Baader's advanced coating processes and sealed edges. This prevents degradation from moisture and aging, ensuring the filter's bandpass remains stable for years. For long-term research projects, this stability is non-negotiable, as it eliminates the filter itself as a source of measurement error.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003e8 Filter Formats: From 1.25\" Mounted to 100x100mm Unmounted\u003c\/h3\u003e\n\u003cp\u003eBaader provides the SLOAN\/SDSS r' filter in a comprehensive range of sizes to integrate with virtually any astronomical imaging system. This ensures that you can maintain photometric consistency whether you are using a small guide scope or a large research-grade reflector.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eRound Mounted (1.25\" \u0026amp; 2\"):\u003c\/strong\u003e Ready to thread into any standard filter wheel or accessory, ideal for most amateur and semi-pro setups.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRound Unmounted (31mm \u0026amp; 36mm):\u003c\/strong\u003e The standard for dedicated astronomy cameras with integrated filter wheels, providing a larger clear aperture to prevent vignetting with fast optical systems.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLarge Format (50mm Round, 50x50mm, 65x65mm, \u0026amp; 100x100mm Square):\u003c\/strong\u003e Designed for cameras with full-frame or larger sensors, commonly found in university and professional observatories.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is a SLOAN\/SDSS r' filter and why is the Baader filter \"photometric\"?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA \u003cstrong\u003eSLOAN\/SDSS r' filter\u003c\/strong\u003e is an optical filter that transmits a specific band of red light, as defined by the Sloan Digital Sky Survey, a major professional astronomical survey. The Baader filter is designated \u003cstrong\u003e\"photometric\"\u003c\/strong\u003e because it is manufactured to precisely match this scientific standard, allowing astronomers to take brightness measurements (photometry) that are consistent and comparable with data from other observatories worldwide.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader SLOAN\/SDSS r' filter for general astrophotography?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile you can, it's not its primary purpose. The SLOAN\/SDSS r' bandpass is designed for scientific measurement, not for creating visually pleasing images. For standard LRGB imaging, a dedicated red filter from a conventional RGB set will produce better color balance when combined with other channels. This filter's strength is data acquisition, not aesthetics.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I choose the right size Baader SLOAN\/SDSS r' filter for my camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eChoose the filter size that matches your filter wheel and avoids vignetting. Here's a general guide:\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" Mounted:\u003c\/strong\u003e Best for cameras with smaller sensors (up to ~1-inch class).\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36mm Unmounted:\u003c\/strong\u003e Ideal for cameras with APS-C sized sensors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2\" Mounted \/ 50mm Round \/ 50x50mm Square:\u003c\/strong\u003e Necessary for full-frame (35mm) sensors to ensure the sensor corners are fully illuminated.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e65x65mm and 100x100mm:\u003c\/strong\u003e Reserved for large-format scientific cameras used in professional observatories.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the Baader SLOAN\/SDSS r' filter require a specific camera to be effective for photometry?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, the filter will work with any monochrome astronomy camera (CCD or CMOS). The key to photometry is a camera with a linear response to light and low noise. The filter simply ensures that the light reaching the sensor is restricted to the correct scientific bandpass, which is the first step in acquiring reliable data.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow can I use the Baader SLOAN\/SDSS r' filter to measure the brightness of asteroid 4 Vesta?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYou would take a series of timed exposures of the star field containing asteroid 4 Vesta. Using photometry software, you measure the brightness of Vesta relative to several nearby reference stars of known, stable magnitude in the same images. Because the Baader SLOAN\/SDSS r' filter ensures you are measuring in a standard bandpass, your resulting magnitude measurement for Vesta can be accurately compared to official databases and other observers' work.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the unmounted 36mm Baader SLOAN\/SDSS r' filter fit my ZWO filter wheel?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The 36mm unmounted filter size is a standard format specifically for use in filter wheels from manufacturers like ZWO, QHY, and others that are designed to pair with APS-C and smaller format astronomy cameras. The filter is held in the carousel by small screws or a retaining plate, depending on the wheel's design.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric SLOAN\/SDSS r' Bandpass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Formats\u003c\/td\u003e\n\u003ctd\u003e1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Filter)\u003cbr\u003e0.03 (65x65mm Square Filter)\u003cbr\u003e0.08 (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Filter)\u003cbr\u003e65 x 65 mm (65x65mm Square Filter)\u003cbr\u003e100 x 100 mm (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eSLOAN, CMOS, CCD\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eSLOAN-r'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to SLOAN-Specification\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Photometric SLOAN\/SDSS r' Filter (in selected size)\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eFilter Protection Case\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967923351837,"sku":"BAA-2961700R","price":217.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967923384605,"sku":"BAA-2961703R","price":363.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967923417373,"sku":"BAA-2961701R","price":272.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967923450141,"sku":"BAA-2961702R","price":290.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967923482909,"sku":"BAA-2961704R","price":436.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Filter","offer_id":44967923515677,"sku":"BAA-2961705R","price":509.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Filter","offer_id":44967923548445,"sku":"BAA-2961706R","price":625.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Filter","offer_id":44967923581213,"sku":"BAA-2961707R","price":1008.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/1635880327.1280.1280__60132.1635880406.1280.1280.jpg?v=1684347064"},{"product_id":"baader-photometric-sloan-sdss-i-individual-filter","title":"Baader Photometric SLOAN\/SDSS i' Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eSLOAN\/SDSS i' Standard:\u003c\/strong\u003e Conforms to the standardized Sloan Digital Sky Survey photometric system for consistent, comparable scientific data.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePhotometric Grade:\u003c\/strong\u003e Engineered for the highest level of optical uniformity, critical for accurate brightness measurements of celestial objects.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNear-Infrared Passband:\u003c\/strong\u003e Isolates a specific portion of the near-infrared spectrum, essential for studying cool stars, distant galaxies, and reducing the effects of light pollution.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMultiple Formats:\u003c\/strong\u003e Available in eight common sizes, including 1.25\" and 2\" mounted filters and unmounted options up to 100x100mm for diverse filter wheels and camera systems.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n  \u003cdiv class=\"DAV-bg-light\"\u003e\n    \u003cdiv class=\"DAV-section-center\"\u003e\n      \u003ch2\u003eBaader Photometric SLOAN\/SDSS i' Individual Filter\u003c\/h2\u003e\n      \u003cp\u003eThe Baader Photometric SLOAN\/SDSS i' Filter is an essential scientific tool for amateur and professional astronomers engaged in photometry. Designed to precisely match the i'-band of the Sloan Digital Sky Survey's photometric system, this filter enables you to collect accurate, repeatable brightness measurements that are directly comparable to data from major astronomical surveys. It isolates a key region of the near-infrared spectrum, making it indispensable for variable star observation, supernova searches, and exoplanet transit analysis.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv class=\"DAV-bg-light\"\u003e\n    \u003cdiv class=\"DAV-section\"\u003e\n      \u003ch3\u003eThe SLOAN\/SDSS i' Standard: Near-Infrared Data for Scientific Analysis\u003c\/h3\u003e\n      \u003cp\u003eThis filter isn't for creating color composites; its purpose is purely scientific data acquisition. The SLOAN i' band is centered in the near-infrared, a critical window for observing cooler, redder objects like M-dwarf stars and for peering through the interstellar dust that obscures visible light. By adhering strictly to this professional standard, your measurements of a variable star's light curve or a distant galaxy's brightness can be reliably compared and contributed to global astronomical databases.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv class=\"DAV-bg-light\"\u003e\n    \u003cdiv class=\"DAV-section\"\u003e\n      \u003ch3\u003eBaader's Photometric Grade Construction\u003c\/h3\u003e\n      \u003cp\u003eA filter labeled \"photometric\" must meet standards far beyond those of a typical imaging filter. Baader ensures each SLOAN\/SDSS i' filter is manufactured with a plano-optically polished substrate, guaranteeing that the filter itself does not introduce optical aberrations or distort the incoming wavefront. This uniformity across the entire filter surface is crucial for ensuring that every star in your field of view is measured with the same accuracy, a non-negotiable requirement for reliable scientific results.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n\u003c\/div\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the Baader SLOAN\/SDSS i' filter primarily used for?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe Baader SLOAN\/SDSS i' filter is designed for \u003cstrong\u003ephotometry\u003c\/strong\u003e—the scientific measurement of the brightness of celestial objects. Its primary applications include tracking the light curves of variable stars, measuring supernova brightness, analyzing exoplanet transits, and contributing data to astronomical surveys that use the standardized Sloan system.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the Baader i' band filter differ from a standard Red or Luminance filter?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eA standard Red or Luminance (L) filter has a very broad transmission profile designed to capture as much light as possible for aesthetically pleasing images. The \u003cstrong\u003eBaader SLOAN\/SDSS i' filter\u003c\/strong\u003e has a much narrower, precisely defined passband in the near-infrared. This precision is what makes scientific measurement possible, but it is not intended for creating conventional LRGB color images.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Baader SLOAN\/SDSS i' filter suitable for visual observing?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eNo, this filter is not recommended for visual use. Its passband is in the near-infrared, a region where the human eye has very low sensitivity. Objects viewed through it would appear extremely dim or be completely invisible. It is designed exclusively for use with monochrome CCD or CMOS astronomy cameras.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is this Baader filter described as \"photometric\"?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eA filter is designated as \u003cstrong\u003ephotometric grade\u003c\/strong\u003e when it meets stringent requirements for optical quality. This includes:\u003c\/p\u003e\n    \u003cul\u003e\n      \u003cli\u003e\n\u003cstrong\u003eSubstrate Uniformity:\u003c\/strong\u003e The glass is plano-optically polished to be perfectly flat, preventing any distortion of the light passing through it.\u003c\/li\u003e\n      \u003cli\u003e\n\u003cstrong\u003eStandardized Passband:\u003c\/strong\u003e The filter's transmission curve strictly adheres to the established scientific standard (in this case, SLOAN\/SDSS i').\u003c\/li\u003e\n    \u003c\/ul\u003e\n    \u003cp\u003eThis ensures that brightness measurements are accurate and repeatable across different telescopes and observatories.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Baader SLOAN\/SDSS i' filter to study the light curve of an eclipsing binary like Algol (Beta Persei)?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eTo study Algol's light curve with the Baader SLOAN\/SDSS i' filter, you would use a monochrome camera to take a series of timed exposures over the course of the eclipse. The i' filter ensures you are measuring a consistent slice of the star's light. By comparing Algol's brightness to nearby, non-variable stars in the same frames, you can plot its change in magnitude over time, revealing the precise moments the companion star begins to block its light.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader SLOAN\/SDSS i' filter to measure the brightness of red carbon stars with my 11\" SCT?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eYes, an 11\" SCT is an excellent instrument for this task, and the Baader i' filter is ideal. Carbon stars are very rich in near-infrared light, where the i' band is located. This filter will provide high-contrast data, allowing you to accurately measure their brightness and track their variability, which is often most pronounced at these wavelengths.\u003c\/p\u003e\n  \u003c\/div\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric SLOAN\/SDSS i'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Formats\u003c\/td\u003e\n\u003ctd\u003e1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Filter)\u003cbr\u003e0.03 (65x65mm Square Filter)\u003cbr\u003e0.08 (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Filter)\u003cbr\u003e65 x 65 mm (65x65mm Square Filter)\u003cbr\u003e100 x 100 mm (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eSLOAN, CMOS, CCD\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eSLOAN-i'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to SLOAN-Specification\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n  \u003cul class=\"DAV-grid\"\u003e\n    \u003cli class=\"DAV-grid-item\"\u003e\n      \u003cdiv\u003e\n        \u003cp class=\"DAV-item-title\"\u003eBaader Photometric SLOAN\/SDSS i' Filter\u003c\/p\u003e\n        \u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n      \u003c\/div\u003e\n    \u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967923679517,"sku":"BAA-2961700I","price":212.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967923712285,"sku":"BAA-2961703I","price":357.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967923745053,"sku":"BAA-2961701I","price":272.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967923777821,"sku":"BAA-2961702I","price":284.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967923810589,"sku":"BAA-2961704I","price":430.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Filter","offer_id":44967923843357,"sku":"BAA-2961705I","price":503.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Filter","offer_id":44967923876125,"sku":"BAA-2961706I","price":619.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Filter","offer_id":44967923908893,"sku":"BAA-2961707I","price":1011.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/1635880476.1280.1280.jpg?v=1684347067"},{"product_id":"baader-photometric-sloan-sdss-z-s-individual-filter","title":"Baader Photometric SLOAN\/SDSS z-s' Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003ePhotometric filter for the SLOAN\/SDSS z-s' bandpass\u003c\/li\u003e\n\u003cli\u003eConforms to the Sloan Digital Sky Survey photometric system standard\u003c\/li\u003e\n\u003cli\u003eEnables calibrated, scientific-grade data acquisition\u003c\/li\u003e\n\u003cli\u003eIdeal for exoplanet transits, variable star monitoring, and photometry of faint objects\u003c\/li\u003e\n\u003cli\u003eAvailable in 8 formats from 1.25\" mounted to 100x100mm unmounted\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric SLOAN\/SDSS z-s' Individual Filter\u003c\/h2\u003e\n\u003cp\u003eThe Baader Photometric SLOAN\/SDSS z-s' Filter is a specialized optical tool designed for research-grade data acquisition in the near-infrared. By precisely matching the z-s' bandpass of the Sloan Digital Sky Survey photometric system, this filter allows astronomers to produce calibrated, repeatable measurements that are directly comparable to professional survey data. Offered in eight distinct formats, from 1.25\" round mounted to 100x100mm square unmounted, the Baader z-s' filter integrates seamlessly into imaging systems ranging from advanced amateur setups to observatory-class instruments.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eSLOAN\/SDSS z-s' Standard: Calibrated Photometry in the Near-Infrared\u003c\/h3\u003e\n\u003cp\u003eThis filter's transmission curve is engineered to isolate the specific near-infrared wavelength range defined by the SLOAN\/SDSS z-s' standard. This adherence to a universal system is critical for scientific applications, as it removes the guesswork from data analysis. Your measurements of variable stars, supernova light curves, or exoplanet transits can be reliably cross-referenced with global astronomical databases.\u003c\/p\u003e\n\u003cp\u003eThe z-s' band is particularly effective for observing cooler, redder stars and highly redshifted distant galaxies. For serious imagers, using a filter calibrated to this standard is the difference between taking a picture and collecting scientific data. It ensures that every photon captured contributes to a valid, publishable measurement.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eMultiple Formats for Diverse Optical Systems\u003c\/h3\u003e\n\u003cp\u003eBaader offers the SLOAN\/SDSS z-s' filter in a comprehensive range of sizes to accommodate virtually any telescope and camera combination. This ensures that you can maintain photometric consistency whether you are using a small refractor or a large Ritchey-Chrétien telescope.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eStandard Mounted Filters (1.25\" \u0026amp; 2\"):\u003c\/strong\u003e These thread directly into standard filter wheels and accessories, making them a plug-and-play solution for most amateur telescopes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnmounted Round Filters (31mm, 36mm, 50mm):\u003c\/strong\u003e These sizes are designed for popular astronomy camera filter wheels, providing a perfect fit while minimizing the potential for vignetting with larger sensors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnmounted Square Filters (50x50mm, 65x65mm, 100x100mm):\u003c\/strong\u003e Intended for large-format CCD and CMOS cameras found in professional and university observatories, these filters provide full illumination for the largest sensors on the market.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the Baader SLOAN\/SDSS z-s' filter used for?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Baader z-s' filter is a scientific instrument used for \u003cstrong\u003ephotometry\u003c\/strong\u003e—the precise measurement of an object's brightness. Its primary applications include tracking the light curves of variable stars, detecting the dip in starlight caused by an exoplanet transit, and measuring the brightness of supernovae and other transient astronomical events in the near-infrared spectrum.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is the \"photometric\" designation important for the Baader z-s' filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA \"photometric\" filter guarantees that its light transmission profile strictly adheres to a scientifically recognized standard, in this case, the \u003cstrong\u003eSloan Digital Sky Survey (SDSS)\u003c\/strong\u003e system. This ensures that data collected with this filter can be accurately calibrated and compared with data from other observers and professional surveys worldwide, making your results scientifically valid.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhich size of the Baader z-s' filter do I need for my imaging setup?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe correct size depends on your filter wheel and camera sensor.\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" and 31mm filters\u003c\/strong\u003e are suitable for cameras with smaller sensors (e.g., Four Thirds format).\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2\" and 36mm filters\u003c\/strong\u003e are recommended for cameras with APS-C sized sensors to prevent vignetting.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e50mm round or 50x50mm square filters\u003c\/strong\u003e (and larger) are necessary for full-frame and larger professional sensors to ensure the entire sensor is evenly illuminated.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader SLOAN\/SDSS z-s' filter for visual observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this filter is designed exclusively for instrumental measurement with CCD or CMOS cameras. Its bandpass is in the near-infrared, where the human eye has very little sensitivity. It will not produce a useful visual image and is not intended for looking through an eyepiece.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would the Baader z-s' filter help in observing a variable M-dwarf star like Proxima Centauri?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eM-dwarf stars are cool, red stars that emit a significant portion of their light in the near-infrared. The \u003cstrong\u003eBaader z-s' filter\u003c\/strong\u003e is optimized for this part of the spectrum, allowing a camera to capture maximum signal from the star while rejecting other wavelengths. This results in a higher signal-to-noise ratio and more precise measurements of the star's brightness variations, which is essential for studying stellar flares or potential transits.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI'm trying to confirm an exoplanet transit with my 11\" SCT. Why is the Baader SLOAN z-s' filter a better choice than a standard infrared-pass filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile a generic IR-pass filter lets in infrared light, its cutoff wavelengths are not standardized. The \u003cstrong\u003eBaader SLOAN z-s' filter\u003c\/strong\u003e has a precisely defined bandpass that matches a scientific standard. When you measure the small dip in brightness during an exoplanet transit, using the z-s' filter allows your data to be directly compared to, and combined with, research from professional observatories, adding significant scientific weight to your confirmation.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Standard\u003c\/td\u003e\n\u003ctd\u003eSLOAN\/SDSS z-s'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBandpass\u003c\/td\u003e\n\u003ctd\u003eNear-Infrared (NIR)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Formats\u003c\/td\u003e\n\u003ctd\u003e1.25\" Round Mounted, 2\" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Filter)\u003cbr\u003e0.03 (65x65mm Square Filter)\u003cbr\u003e0.08 (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Filter)\u003cbr\u003e65 x 65 mm (65x65mm Square Filter)\u003cbr\u003e100 x 100 mm (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eSLOAN, CMOS, CCD\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eSLOAN-z-s'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to SLOAN-Specification\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Photometric SLOAN\/SDSS z-s' Filter (Selected Size)\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eFilter Case\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967924007197,"sku":"BAA-2961700Z","price":204.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967924039965,"sku":"BAA-2961703Z","price":350.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967924072733,"sku":"BAA-2961701Z","price":259.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967924105501,"sku":"BAA-2961702Z","price":277.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967924138269,"sku":"BAA-2961704Z","price":423.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Filter","offer_id":44967924171037,"sku":"BAA-2961705Z","price":495.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Filter","offer_id":44967924203805,"sku":"BAA-2961706Z","price":612.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Filter","offer_id":44967924236573,"sku":"BAA-2961707Z","price":1014.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/1635880476.1280.1280__62550.1635880703.1280.1280.jpg?v=1684347071"},{"product_id":"baader-photometric-sloan-sdss-y-individual-filter","title":"Baader Photometric SLOAN\/SDSS y' Individual Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eConforms to the SLOAN\/SDSS y' photometric standard\u003c\/li\u003e\n\u003cli\u003eDesigned for scientific magnitude measurements\u003c\/li\u003e\n\u003cli\u003eIdeal for variable star and exoplanet transit research\u003c\/li\u003e\n\u003cli\u003eAvailable in multiple mounted and unmounted sizes\u003c\/li\u003e\n\u003cli\u003eFeatures planeoptically polished surfaces for maximum sharpness\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eBaader Photometric SLOAN\/SDSS y' Individual Filter\u003c\/h2\u003e\n\u003cp\u003eThe Baader Photometric SLOAN\/SDSS y' Individual Filter is a specialized optical component designed for rigorous scientific imaging and data collection. This filter precisely isolates the y'-band wavelength range as defined by the Sloan Digital Sky Survey, enabling astronomers to capture accurate, repeatable brightness measurements for astrophysical research. Its construction ensures the optical integrity required for serious photometry, from university-level projects to advanced amateur variable star observing programs.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe SLOAN\/SDSS y' Bandpass for Scientific Imaging\u003c\/h3\u003e\n\u003cp\u003eThis filter is not intended for general visual observation or aesthetic color imaging; its sole purpose is instrumental measurement. By conforming to the standardized SLOAN\/SDSS system, your data becomes directly comparable to professional survey results and other observers' work worldwide. The y'-band is particularly useful for studying cool stars, brown dwarfs, and distant, redshifted objects.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlaneoptically Polished Substrate:\u003c\/strong\u003e Each filter is polished to an exacting standard, preventing any degradation of your telescope's optical resolution. This ensures that point sources remain sharp, which is critical for accurate magnitude extraction from crowded star fields.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMulti-Layer Dielectric Coatings:\u003c\/strong\u003e Advanced coatings provide a hard, scratch-resistant surface while ensuring high transmission within the target bandpass and deep rejection of out-of-band light. This maximizes signal-to-noise ratio for faint targets.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHomofocal Design:\u003c\/strong\u003e When used with other Baader photometric filters, the y' filter is designed to be homofocal, minimizing the need to refocus when switching between filters during an imaging sequence.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the primary use of the Baader Photometric SLOAN\/SDSS y' filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe primary use of the \u003cstrong\u003eBaader SLOAN\/SDSS y' filter\u003c\/strong\u003e is for scientific photometry. This involves precisely measuring the brightness of celestial objects like variable stars, asteroids, supernovae, and transiting exoplanets. It is designed to conform to the Sloan Digital Sky Survey (SDSS) filter system, ensuring your measurements are standardized and comparable to professional data.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Baader SLOAN\/SDSS y' filter good for visual observing or regular color astrophotography?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this is a highly specialized scientific filter. Its narrow, specific bandpass is designed for measurement, not for creating visually pleasing or \"true-color\" images. For general deep-sky imaging, you would use LRGB or narrowband filters. For visual use, this filter would produce a dim, oddly colored image with little aesthetic value.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Baader y' filter to study an exoplanet transit around a star like TRAPPIST-1?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eTo study an exoplanet transit, you would use a monochrome camera and take a continuous series of images of the host star (like the red dwarf TRAPPIST-1) through the \u003cstrong\u003eBaader y' filter\u003c\/strong\u003e before, during, and after the predicted transit time. The y'-band is effective for red dwarfs. By measuring the star's brightness in each frame, you can plot a light curve showing the slight dip in brightness as the planet passes in front, allowing you to confirm the transit and measure its depth.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader SLOAN\/SDSS y' filter to create a light curve of an asteroid like 4 Vesta?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, absolutely. You would image the asteroid 4 Vesta repeatedly over several hours using the \u003cstrong\u003eBaader y' filter\u003c\/strong\u003e and a monochrome camera. By measuring Vesta's brightness relative to nearby, non-variable field stars in each image, you can plot its change in magnitude over time. This light curve reveals the asteroid's rotation period and can provide clues about its shape.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat makes this Baader filter \"photometric\"?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA \"photometric\" filter has several key characteristics:\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eStandardized Bandpass:\u003c\/strong\u003e It accurately reproduces a specific bandpass from a recognized system, in this case, the SLOAN\/SDSS y'-band.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExcellent Transmission:\u003c\/strong\u003e It allows a very high percentage of light within that bandpass to reach the sensor.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStrong Out-of-Band Blocking:\u003c\/strong\u003e It aggressively rejects all wavelengths outside the specified bandpass.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOptical Quality:\u003c\/strong\u003e The filter substrate is planeoptically polished so it does not distort the image.\u003c\/li\u003e\n\u003c\/ul\u003e\nThese features ensure that brightness measurements are accurate, repeatable, and comparable between different observers and instruments.\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy are there so many size options for the Baader Photometric y' filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe different sizes accommodate the vast range of astronomical equipment.\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" and 2\" Mounted:\u003c\/strong\u003e These are for standard eyepiece-filter wheels and filter drawers.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e31mm and 36mm Unmounted:\u003c\/strong\u003e These are common sizes for filter wheels used with smaller-format astronomy cameras.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e50mm Round, 50x50mm, 65x65mm, and 100x100mm Square:\u003c\/strong\u003e These larger unmounted filters are for filter wheels designed for cameras with large full-frame or medium-format sensors, preventing vignetting on wide fields of view.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric SLOAN\/SDSS y'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" Mounted, 2\" Mounted, 31mm Unmounted, 36mm Unmounted, 50mm Round Unmounted, 50x50mm Square, 65x65mm Square, 100x100mm Square\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01 (1.25\" Round Mounted, 2\" Round Mounted, 50mm Round Unmounted)\u003cbr\u003e0.02 (50x50mm Square Filter)\u003cbr\u003e0.03 (65x65mm Square Filter)\u003cbr\u003e0.08 (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch (1.25\" Round Mounted)\u003cbr\u003e2 inch (2\" Round Mounted)\u003cbr\u003e36 mm (36mm Round Unmounted)\u003cbr\u003e50.4 mm (50mm Round Unmounted)\u003cbr\u003e50 x 50 mm (50x50mm Square Filter)\u003cbr\u003e65 x 65 mm (65x65mm Square Filter)\u003cbr\u003e100 x 100 mm (100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter shape\u003c\/td\u003e\n\u003ctd\u003eround (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted, 50mm Round Unmounted)\u003cbr\u003esquare (50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSingle or Set?\u003c\/td\u003e\n\u003ctd\u003eSingle Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter mounted\u003c\/td\u003e\n\u003ctd\u003eMounted (LPFC 6mm) (1.25\" Round Mounted, 2\" Round Mounted)\u003cbr\u003eUnmounted (36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Usage\u003c\/td\u003e\n\u003ctd\u003eSLOAN, CMOS, CCD\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecial Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness (without cell)\u003c\/td\u003e\n\u003ctd\u003e2 mm (1.25\" Round Mounted, 2\" Round Mounted, 36mm Round Unmounted)\u003cbr\u003e3 mm (50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCWL (Central Wavelength)\u003c\/td\u003e\n\u003ctd\u003eSLOAN-y'\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission Range\u003c\/td\u003e\n\u003ctd\u003eTransmission according to SLOAN-Specification\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAR-Coating\u003c\/td\u003e\n\u003ctd\u003eReflex-Blocker™ hard coated, planeoptically polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSuitable for f\/ratio\u003c\/td\u003e\n\u003ctd\u003ef\/15 to f\/1.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003cp style=\"text-align: center;\"\u003eThis product is a single filter. No additional accessories are included.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Baader_Planetarium_Cleaning_and_Maintenance_of_Optics_Manual.pdf\" target=\"_blank\"\u003e\u003csvg class=\"DAV-img-box\" viewbox=\"0 0 512 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"\u003e\u003cpath d=\"M0 64C0 28.7 28.7 0 64 0L224 0l0 128c0 17.7 14.3 32 32 32l128 0 0 144-208 0c-35.3 0-64 28.7-64 64l0 144-48 0c-35.3 0-64-28.7-64-64L0 64zm384 64l-128 0L256 0 384 128zM176 352l32 0c30.9 0 56 25.1 56 56s-25.1 56-56 56l-16 0 0 32c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-48 0-80c0-8.8 7.2-16 16-16zm32 80c13.3 0 24-10.7 24-24s-10.7-24-24-24l-16 0 0 48 16 0zm96-80l32 0c26.5 0 48 21.5 48 48l0 64c0 26.5-21.5 48-48 48l-32 0c-8.8 0-16-7.2-16-16l0-128c0-8.8 7.2-16 16-16zm32 128c8.8 0 16-7.2 16-16l0-64c0-8.8-7.2-16-16-16l-16 0 0 96 16 0zm80-112c0-8.8 7.2-16 16-16l48 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 32 32 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 48c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-64 0-64z\" fill=\"#0047a7\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader Planetarium Cleaning and Maintenance of Optics Manual\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003eCleaning \u0026amp; Maintenance\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Round Mounted","offer_id":44967924334877,"sku":"BAA-2961700Y","price":206.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967924367645,"sku":"BAA-2961703Y","price":351.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967924400413,"sku":"BAA-2961701Y","price":259.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967924433181,"sku":"BAA-2961702Y","price":279.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967924465949,"sku":"BAA-2961704Y","price":424.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Filter","offer_id":44967924498717,"sku":"BAA-2961705Y","price":497.0,"currency_code":"CAD","in_stock":true},{"title":"65x65mm Square Filter","offer_id":44967924531485,"sku":"BAA-2961706Y","price":613.0,"currency_code":"CAD","in_stock":true},{"title":"100x100mm Square Filter","offer_id":44967924564253,"sku":"BAA-2961707Y","price":1017.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/1635880770.1280.1280.jpg?v=1684347070"}],"url":"https:\/\/davidastro.com\/collections\/baader-scientific-and-photometric-filters.oembed","provider":"David Astro","version":"1.0","type":"link"}