{"title":"Baader UBVRI Photometric Filters","description":"\u003cp\u003eBaader Photometric UBVRI filters follow the Johnson-Cousins UBVRI system used for standard stellar photometry. They allow amateur and research observatories to measure brightness and colour indices that can be compared with catalogue values and professional results.\u003c\/p\u003e\u003cp\u003eThe U, B, V, R and I filters are sold individually or as a complete UBVRI set. They are a common choice for variable star monitoring, scientific outreach projects and university teaching labs.\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-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"}],"url":"https:\/\/davidastro.com\/collections\/baader-ubvri-photometric-filters.oembed","provider":"David Astro","version":"1.0","type":"link"}