{"title":"Chroma Bessel UBVRI Photometric Filters","description":"\u003cp\u003eChroma Bessel filters are photometric filters matched to the standard Johnson-Cousins UBVRI system, used to measure star brightness and color in calibrated bands. The line includes individual U, B, V, R and I Bessel filters and a complete UBVRI filter set.\u003c\/p\u003e\u003cp\u003eThey suit observers doing variable star work, exoplanet transit timing, asteroid light curves or student research, where results must be comparable with professional catalogs. Chroma's hard-coated interference filters give stable passbands over time, an important point for long photometric programs.\u003c\/p\u003e","products":[{"product_id":"chroma-u-bessel-filter","title":"Chroma U-Bessell Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eBessell U-Band Photometric Filter\u003c\/li\u003e\n\u003cli\u003e3.0 mm Substrate Thickness\u003c\/li\u003e\n\u003cli\u003eParfocal with other Chroma Astronomy Filters (except LoGlow)\u003c\/li\u003e\n\u003cli\u003eTransmitted Wavefront better than 0.25 waves\/inch\u003c\/li\u003e\n\u003cli\u003eDurable Sputtered Hard Coatings\u003c\/li\u003e\n\u003cli\u003eMade in Vermont, USA\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\u003eChroma U-Bessell Filter\u003c\/h2\u003e\n\u003cp\u003eThe Chroma U-Bessell Filter is built on a uniform 3.0 mm thick, single-glass substrate for parfocal consistency when used with other filters in the \u003ca href=\"\/en-us\/products\/chroma-ubvri-filter-set\"\u003eChroma UBVRI\u003c\/a\u003e series. With a transmitted wavefront better than 0.25 waves\/inch, this filter is built for ultraviolet photometry in the Bessell UBVRI system.\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-Bessell Standard: Foundational UV Data for Photometry\u003c\/h3\u003e\n\u003cp\u003eThis filter isolates the ultraviolet (U) portion of the spectrum matching the Bessell realization of the Johnson-Cousins UBVRI photometric system, commonly used in professional and academic astronomy. By capturing this specific UV window, you can perform scientific analysis such as determining the temperature of hot, young stars, studying accretion disks around compact objects, and measuring the light curves of variable stars and supernovae.\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\u003e3.0mm Parfocal Design, Better Than 0.25 Waves\/Inch Wavefront\u003c\/h3\u003e\n\u003cp\u003eEvery Chroma astronomy filter is manufactured in Vermont, USA, using durable sputtered hard coatings on a single 3.0 mm substrate. The construction has no laminations, and Chroma tests its sputtered coatings for abrasion, humidity and temperature exposure. The 3.0 mm thickness makes the filter parfocal with other Chroma astronomy filters (except LoGlow), eliminating the need to refocus when switching between them in a \u003ca href=\"\/en-us\/collections\/filter-wheels\"\u003efilter wheel\u003c\/a\u003e.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSputtered Hard Coatings:\u003c\/strong\u003e Applied by reactive magnetron sputtering for durability, with an anti-reflection coating on the rear surface to prevent ghosting.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eParfocal Consistency:\u003c\/strong\u003e The standardized 3.0 mm thickness means you can swap between U, B, V, R, and I filters without losing focus, saving critical time during an imaging sequence.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOptical Precision:\u003c\/strong\u003e A transmitted wavefront better than 0.25 waves\/inch helps preserve the performance of your telescope's optics.\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 Chroma U-Bessell filter primarily used for?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003eChroma U-Bessell filter\u003c\/strong\u003e is designed for scientific photometry. It isolates the ultraviolet (UV) band of the standard UBVRI system, allowing astronomers to accurately measure the brightness and color of celestial objects to determine physical properties like temperature and composition.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Chroma U-Bessell filter parfocal with other filters?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. It is manufactured on a \u003cstrong\u003e3.0 mm thick substrate\u003c\/strong\u003e, making it parfocal with all other Chroma astronomy filters (with the exception of the LoGlow filter). This means you can switch between filters in a filter wheel without needing to refocus your telescope.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does a transmitted wavefront of \"better than 0.25 waves\/inch\" mean for my images?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIt describes how little the filter distorts light passing through it. A transmitted wavefront better than 0.25 waves per inch means the \u003cstrong\u003eChroma U-Bessell filter\u003c\/strong\u003e adds very little wavefront error, which helps preserve the sharpness of your telescope's optics.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the construction of the Chroma U-Bessell filter improve its durability?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eChroma uses \u003cstrong\u003edurable sputtered hard coatings\u003c\/strong\u003e on a single, non-laminated glass substrate. This method creates an extremely resilient surface that resists humidity, temperature changes, and routine cleaning.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Chroma U-Bessell filter with a fast telescope like an f\/2 system?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eChroma does not publish a focal-ratio rating or f\/# data for its photometric filters. All interference filters shift toward the blue in fast beams; a broadband filter is less affected than a narrowband one, but for strict photometry, check with Chroma before using a very fast system.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the difference between mounted and unmounted versions of the Chroma U-Bessell filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003e\u003cstrong\u003eMounted filters\u003c\/strong\u003e (1.25\" and 2\") come in a threaded ring (M28.5x0.6 and M48x0.75 respectively) ready to be screwed into a filter wheel or \u003ca href=\"\/en-us\/collections\/eyepieces\"\u003eeyepiece\u003c\/a\u003e. \u003cstrong\u003eUnmounted filters\u003c\/strong\u003e (31mm, 36mm, 50mm round, and 50x50mm square) are bare glass intended for \u003ca href=\"\/en-us\/collections\/filter-wheels-and-drawers\"\u003efilter drawers\u003c\/a\u003e or wheels that use retaining rings to hold the filter in place.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhen would I use the U-Bessell filter instead of a B or V filter for observing a variable star like Algol (Beta Persei)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eFor a hot, blue star like Algol, the greatest variation in brightness occurs in the ultraviolet and blue parts of the spectrum. The \u003cstrong\u003eU-Bessell filter\u003c\/strong\u003e would capture the most dramatic changes in its light curve during an eclipse. The B (Blue) and V (Visual\/Green) filters would show progressively less variation, providing color information that reveals temperature changes as the secondary star passes in front of the primary.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the Chroma U-Bessell filter come with a warranty?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. All Chroma sputtered catalog filters, including the U-Bessell, are covered by the \u003cstrong\u003eChroma lifetime warranty\u003c\/strong\u003e against manufacturing defects under normal use. They are manufactured in Vermont, USA.\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\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eChroma Technology Corp\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePart Number\u003c\/td\u003e\n\u003ctd\u003e27050\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003eBessell U-Band Photometric\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 unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCell Thread (Mounted)\u003c\/td\u003e\n\u003ctd\u003e1.25\": M28.5x0.6 male; 2\": M48x0.75 male\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Thickness\u003c\/td\u003e\n\u003ctd\u003e3.0 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eParfocal\u003c\/td\u003e\n\u003ctd\u003eYes, with other 3.0mm Chroma astronomy filters\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eDurable sputtered hard coatings\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoating Application\u003c\/td\u003e\n\u003ctd\u003ePrimary coating on front surface, AR coating on rear surface\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eConstruction\u003c\/td\u003e\n\u003ctd\u003eSingle, non-laminated substrate\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmitted Wavefront\u003c\/td\u003e\n\u003ctd\u003eBetter than 0.25 waves\/inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCountry of Origin\u003c\/td\u003e\n\u003ctd\u003eVermont, USA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWarranty\u003c\/td\u003e\n\u003ctd\u003eChroma Lifetime Warranty\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\"\u003eChroma U-Bessell 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\u003ca href=\"https:\/\/www.chroma.com\/resources\/customer-support\/warranty-information\/\" rel=\"noopener\" target=\"_blank\"\u003eChroma Technology Lifetime Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Chroma","offers":[{"title":"1.25\" Round Mounted","offer_id":44967249051933,"sku":"CT-27050-1.25M","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967249084701,"sku":"CT-27050-31D","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967249117469,"sku":"CT-27050-36D","price":483.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967249150237,"sku":"CT-27050-2M","price":980.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967249183005,"sku":"CT-27050-50D","price":910.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967249215773,"sku":"CT-27050-50X50","price":1015.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Transmission-Curve-of-Chroma-U-Bessel-Filter__84625.1596071523.1280.1280.jpg?v=1684339524"},{"product_id":"chroma-v-bessel-filter","title":"Chroma V-Bessell Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eStandard V-Bessell photometric filter for scientific measurement\u003c\/li\u003e\n\u003cli\u003e3.0 mm thick substrate ensures parfocality with other Chroma filters\u003c\/li\u003e\n\u003cli\u003eTransmitted wavefront better than 0.25 waves\/inch\u003c\/li\u003e\n\u003cli\u003eDurable, sputtered hard coatings with anti-reflection on the rear surface\u003c\/li\u003e\n\u003cli\u003eAvailable in 1.25\" and 2\" mounted, and 31mm, 36mm, 50mm, and 50x50mm unmounted formats\u003c\/li\u003e\n\u003cli\u003eMade in Vermont, USA with a lifetime warranty\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\u003eChroma V-Bessell Filter\u003c\/h2\u003e\n\u003cp\u003eThe Chroma V-Bessell Filter is manufactured on a 3.0 mm thick glass substrate, ensuring it is parfocal with other Chroma astronomy filters. It uses durable sputtered hard coatings and has a transmitted wavefront better than 0.25 waves\/inch. Available in multiple formats including 1.25\" (M28.5x0.6) and 2\" (M48x0.75) mounted cells, this filter matches the Bessell realization of the Johnson-Cousins UBVRI photometric system.\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 V-Bessell Band: A Standard for Scientific Photometry\u003c\/h3\u003e\n\u003cp\u003eThis is not an aesthetic color filter; it is a scientific instrument. The V-Bessell filter isolates the \"Visual\" green-yellow portion of the spectrum matching the Bessell realization of the Johnson-Cousins UBVRI photometric system. Its precise bandpass allows you to take repeatable, scientifically valid measurements of stellar brightness (V magnitude), making it essential for variable star observation, exoplanet transit timing, and supernova light curve analysis.\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\u003eBuilt for Data Integrity: 3.0mm Parfocal Substrate \u0026amp; Better Than 0.25 Waves\/Inch Wavefront\u003c\/h3\u003e\n\u003cp\u003eThe single 3.0 mm substrate makes the filter parfocal with other Chroma astronomy filters (except the LoGlow), so switching between bands needs little or no refocusing. The transmitted wavefront is better than 0.25 waves\/inch.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSputtered Hard Coatings:\u003c\/strong\u003e Chroma's sputtered coatings are deposited on a single glass substrate and are built to withstand humidity changes and extreme temperature fluxes.\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAnti-Reflection Treatment:\u003c\/strong\u003e The rear surface is anti-reflection coated to prevent ghosting and internal reflections, which can corrupt photometric measurements and contaminate faint targets.\n\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\u003eChoosing Your Format: From 1.25\" to 50mm Square\u003c\/h3\u003e\n\u003cp\u003eThe Chroma V-Bessell filter is available in a range of sizes. Mounted versions in 1.25\" (M28.5x0.6) and 2\" (M48x0.75) formats thread directly into standard \u003ca href=\"\/en-us\/collections\/filter-wheels\"\u003efilter wheels\u003c\/a\u003e and camera nosepieces. Unmounted options are available in 31 mm, 36 mm, 50 mm round, and 50 x 50 mm square sizes; the 50 mm sizes are typically used for full-frame class sensors.\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 Chroma V-Bessell filter primarily used for?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Chroma V-Bessell 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 transiting exoplanets, in the standardized \"V\" (Visual) band of the UBVRI system.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Chroma V-Bessell filter the same as a regular \"Green\" LRGB filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. While both pass green light, they have different purposes. The \u003cstrong\u003eV-Bessell filter\u003c\/strong\u003e has a strictly defined bandpass for scientific measurement. A standard \u003cstrong\u003eLRGB Green filter\u003c\/strong\u003e is designed for aesthetic color balance in astrophotography and has a different transmission curve, which makes it unsuitable for standard photometry.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Chroma V-Bessell filter to measure 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 exposures of Algol through the V-Bessell filter over the course of its eclipse period. By comparing the brightness of Algol to nearby, non-variable stars of known magnitude in the same images, you can plot a light curve that precisely charts its change in brightness. This is a fundamental technique in variable star observation.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the 36mm unmounted Chroma V-Bessell filter work with my APS-C camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eTypically, yes. In a filter wheel built for 36mm filters, the 36mm unmounted size typically suits APS-C class sensors; actual coverage depends on the filter-to-sensor spacing and the focal ratio.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is the 3.0mm thickness of the Chroma V-Bessell filter important?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe uniform \u003cstrong\u003e3.0 mm thickness\u003c\/strong\u003e makes the filter \u003cstrong\u003eparfocal\u003c\/strong\u003e with other Chroma astronomy filters (except their LoGlow filter). This means you can switch between your U, B, V, R, and I filters with little or no refocusing, saving valuable imaging time.\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, B, R, and I filters to use the Chroma V-Bessell?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile the V-Bessell filter is powerful on its own for measuring V-band magnitude, its true scientific potential is realized as part of a complete UBVRI set. Using multiple filters allows you to measure an object's color indices (e.g., B-V), which are critical for determining stellar temperature, age, and classification.\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\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eChroma Technology Corp\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePart Number\u003c\/td\u003e\n\u003ctd\u003e27051\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003ePhotometric (V-Bessell)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Formats\u003c\/td\u003e\n\u003ctd\u003e1.25\" mounted (M28.5x0.6), 2\" mounted (M48x0.75), 31mm unmounted, 36mm unmounted, 50mm unmounted, 50x50mm square\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Thickness\u003c\/td\u003e\n\u003ctd\u003e3.0 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eParfocal\u003c\/td\u003e\n\u003ctd\u003eYes, with other Chroma astronomy filters\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eDurable sputtered hard coatings, AR-coated rear surface\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmitted Wavefront\u003c\/td\u003e\n\u003ctd\u003eBetter than 0.25 waves\/inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCountry of Origin\u003c\/td\u003e\n\u003ctd\u003eVermont, USA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWarranty\u003c\/td\u003e\n\u003ctd\u003eChroma Lifetime Warranty\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\"\u003eChroma V-Bessell 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\u003ca href=\"https:\/\/www.chroma.com\/resources\/customer-support\/warranty-information\/\" rel=\"noopener\" target=\"_blank\"\u003eChroma Lifetime Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Chroma","offers":[{"title":"1.25\" Round Mounted","offer_id":44967249281309,"sku":"CT-27051-1.25M","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967249314077,"sku":"CT-27051-31D","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967249346845,"sku":"CT-27051-36D","price":483.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967249379613,"sku":"CT-27051-2M","price":980.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967249412381,"sku":"CT-27051-50D","price":910.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967249445149,"sku":"CT-27051-50X50","price":1015.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Transmission-Curve-of-Chroma-V-Bessel-Filter__56381.1596071524.1280.1280.jpg?v=1684339526"},{"product_id":"chroma-b-bessel-filter","title":"Chroma B-Bessell Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eStandard B-Bessell photometric filter for UBVRI measurements\u003c\/li\u003e\n\u003cli\u003e3.0 mm thick substrate, parfocal with other Chroma astronomy filters\u003c\/li\u003e\n\u003cli\u003eTransmitted wavefront is better than 0.25 waves\/inch for sharp stellar images\u003c\/li\u003e\n\u003cli\u003eDurable sputtered hard coatings, with a rear anti-reflection coating to prevent ghosting\u003c\/li\u003e\n\u003cli\u003eAvailable in multiple sizes including 1.25\" and 2\" mounted, and 31mm, 36mm, and 50mm 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\u003eChroma B-Bessell Filter\u003c\/h2\u003e\n\u003cp\u003eThe Chroma B-Bessell Filter is a scientific-grade photometric filter built on a 3.0 mm thick substrate for parfocal operation within a UBVRI filter set. Its transmitted wavefront of better than 0.25 waves\/inch preserves the resolution of your optical system for precise stellar measurements. Manufactured in Vermont, USA, this filter uses durable sputtered hard coatings on a single substrate to deliver the standardized blue bandpass required for Johnson-Cousins photometry.\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 Bessell B-Band: A Standard for Johnson-Cousins Photometry\u003c\/h3\u003e\n\u003cp\u003eThis is not a general-purpose \"blue\" filter for RGB imaging; it is a precision instrument for photometry. The Chroma B-Bessell filter isolates the specific blue portion of the spectrum defined by the standard Johnson-Cousins UBVRI system. This allows you to accurately measure the apparent magnitude of celestial objects and calculate their color index (e.g., B-V), a fundamental technique for classifying stars and studying variable star behavior.\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\u003e3.0mm Parfocal Design for UBVRI Filter Sets\u003c\/h3\u003e\n\u003cp\u003eAll Chroma astronomy filters except the LoGlow are built on a 3.0 mm thick single-glass substrate. This uniform thickness is critical for photometry, where you rapidly cycle through different filters in a wheel. The parfocal design means filter thickness does not change focus when you switch between this B-Bessell filter and Chroma's U, V, R, and I filters, saving time in your data acquisition 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\u003eBetter Than 0.25 Waves\/Inch Wavefront and Sputtered Hard Coatings\u003c\/h3\u003e\n\u003cp\u003eThe transmitted wavefront is better than 0.25 waves\/inch, so the filter adds very little wavefront error. This maintains sharp, point-like star images, which is essential for accurate magnitude measurements. The coatings are applied via a durable sputtering process on a single substrate, with an anti-reflection coating on the rear surface to prevent ghosting and internal reflections that could corrupt photometric 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\"\u003eWhat is the primary use for the Chroma B-Bessell Filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Chroma B-Bessell Filter is designed specifically for \u003cstrong\u003escientific photometry\u003c\/strong\u003e. Its purpose is to isolate the standardized \"B\" (blue) bandpass of the Johnson-Cousins UBVRI system, allowing astronomers to accurately measure the brightness and color of stars for research on topics like stellar classification and variability.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Chroma B-Bessell Filter parfocal with other filters?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. It is manufactured on a \u003cstrong\u003e3.0 mm thick substrate\u003c\/strong\u003e, making it parfocal with all other Chroma astronomy filters (with the exception of the LoGlow filter). This means filter thickness does not change focus when you switch between filters in a UBVRI set, which helps efficient data collection.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Chroma B-Bessell Filter for imaging nebulae like the Orion Nebula (M42)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile you can, it is not the ideal tool for that task. The B-Bessell is a wideband filter designed to capture starlight for measurement. For deep-sky objects like the Orion Nebula (M42), you would achieve much higher contrast and reveal more detail by using \u003ca href=\"\/en-us\/collections\/narrowband-filters\"\u003enarrowband filters\u003c\/a\u003e, such as Hydrogen-alpha or Oxygen-III, which isolate the specific wavelengths emitted by the nebula's gases.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat kind of targets would I observe with the Chroma B-Bessell Filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis filter is best used for photometric studies of stars. Excellent targets include:\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eVariable Stars:\u003c\/strong\u003e Measuring the light curve of stars like Algol (Beta Persei) or Delta Cephei as their brightness changes over time.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStar Clusters:\u003c\/strong\u003e Creating a color-magnitude diagram (Hertzsprung-Russell diagram) for a cluster like the Pleiades (M45) to determine its age and distance.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExoplanet Transits:\u003c\/strong\u003e Detecting the slight dimming of a star as a planet passes in front of it.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhich size Chroma B-Bessell filter do I need for my camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe right size avoids vignetting (darkening of the corners); as a typical guide:\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" Mounted:\u003c\/strong\u003e Typically for cameras with smaller sensors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e31mm Unmounted:\u003c\/strong\u003e Typically for smaller sensors in a \u003ca href=\"\/en-us\/collections\/filter-wheels\"\u003efilter wheel\u003c\/a\u003e. \u003cstrong\u003e36mm Unmounted:\u003c\/strong\u003e Typically for APS-C class sensors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e50mm Round\/Square Unmounted:\u003c\/strong\u003e Typically needed for full-frame (35mm) sensors and larger. The 2\" mounted size typically suits APS-C class sensors; vignetting also depends on filter-to-sensor spacing and focal ratio.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does \"sputtered hard coating\" mean for the Chroma B-Bessell Filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIt refers to the manufacturing process where layers of optical material are deposited atom-by-atom onto the 3.0 mm glass substrate. The sputtered coatings withstand humidity changes and temperature extremes and remain spectrally accurate, and Chroma's sputtered catalog filters carry a lifetime warranty.\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\u003eB-Bessell Photometric\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eChroma Technology Corp (Vermont, USA)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChroma Part Number\u003c\/td\u003e\n\u003ctd\u003e27052\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Thickness\u003c\/td\u003e\n\u003ctd\u003e3.0 mm substrate\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eParfocal\u003c\/td\u003e\n\u003ctd\u003eYes, with other Chroma astronomy filters (except LoGlow 27030)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmitted Wavefront\u003c\/td\u003e\n\u003ctd\u003eBetter than 0.25 waves\/inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eDurable sputtered hard coatings on a single substrate\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAnti-Reflection\u003c\/td\u003e\n\u003ctd\u003eCoating on the rear surface\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" mounted, 2\" mounted, 31 mm, 36 mm, 50 mm round unmounted, 50 x 50 mm square unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCell Thread (Mounted)\u003c\/td\u003e\n\u003ctd\u003e1.25\": M28.5x0.6 male; 2\": M48x0.75 male\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMade In\u003c\/td\u003e\n\u003ctd\u003eVermont, USA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWarranty\u003c\/td\u003e\n\u003ctd\u003eChroma lifetime warranty for sputtered catalog filters\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\"\u003eChroma B-Bessell 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\u003ca href=\"https:\/\/www.chroma.com\/resources\/customer-support\/warranty-information\/\" rel=\"noopener\" target=\"_blank\"\u003eChroma Lifetime Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Chroma","offers":[{"title":"1.25\" Round Mounted","offer_id":44967249510685,"sku":"CT-27052-1.25M","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967249543453,"sku":"CT-27052-31D","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967249576221,"sku":"CT-27052-36D","price":483.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967249608989,"sku":"CT-27052-2M","price":980.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967249641757,"sku":"CT-27052-50D","price":910.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967249674525,"sku":"CT-27052-50X50","price":1015.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Transmission-Curve-of-Chroma-B-Bessel-Filter__40887.1596071525.1280.1280.jpg?v=1684339528"},{"product_id":"chroma-r-bessel-filter","title":"Chroma R-Bessell Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eStandardized R-Bessell band for scientific photometry\u003c\/li\u003e\n\u003cli\u003e3.0 mm thick substrate, parfocal with other Chroma astronomy filters (except LoGlow)\u003c\/li\u003e\n\u003cli\u003eTransmitted wavefront better than 0.25 waves per inch\u003c\/li\u003e\n\u003cli\u003eDurable, single-substrate sputtered coatings with AR layer\u003c\/li\u003e\n\u003cli\u003eMade in Vermont, USA with a lifetime warranty\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\u003eChroma R-Bessell Filter\u003c\/h2\u003e\n\u003cp\u003eThe Chroma R-Bessell Filter (part number 27053) provides a standardized red passband for scientific UBVRI photometry, built on a 3.0 mm thick substrate to ensure it remains parfocal with other Chroma astronomy filters. It has a transmitted wavefront better than 0.25 waves\/inch and durable sputtered coatings. Available in multiple formats including 1.25\" (M28.5x0.6 thread) and 2\" (M48x0.75 thread) mounted cells, plus 31 mm, 36 mm and 50 mm round and 50 x 50 mm square unmounted sizes.\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 R-Bessell Band for UBVRI Photometry\u003c\/h3\u003e\n\u003cp\u003eThis filter is not for general-purpose color imaging; it is a scientific instrument designed to conform to the Johnson-Cousins-Bessell UBVRI photometric system. The R-Bessell filter isolates a specific portion of the red spectrum, allowing you to capture stellar brightness data that, after standard calibration, is comparable with other measurements in the same photometric system. This standardization is critical for contributing to pro-am collaborations, monitoring variable stars, tracking supernova light curves, and determining the color index of celestial objects.\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\u003e3.0mm Parfocal Substrates and \u0026lt;0.25 Wave\/Inch Accuracy\u003c\/h3\u003e\n\u003cp\u003eEvery Chroma R-Bessell filter is built on a single, non-laminated 3.0 mm thick glass substrate. It is parfocal with other Chroma astronomy filters (except LoGlow), eliminating the need to refocus when you switch between filters in a wheel and ensuring consistent data acquisition throughout an automated imaging sequence. Transmitted wavefront is better than 0.25 waves per inch.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDurable Sputtered Coatings:\u003c\/strong\u003e The coating is durable and high-transmission, engineered for durability and stability to help ensure consistent performance in long-term projects.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAnti-Reflection Layer:\u003c\/strong\u003e The rear surface features an anti-reflection coating to suppress ghosting and internal reflections, preserving image contrast.\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\u003eSizing for Every Sensor: 1.25\" to 50x50mm Formats\u003c\/h3\u003e\n\u003cp\u003eChroma offers the R-Bessell filter in six sizes. Mounted filters use standard cell threads, with the 1.25\" filter using an M28.5x0.6 thread and the 2\" using an M48x0.75 thread. Unmounted versions fit \u003ca href=\"\/en-us\/collections\/filter-wheels\"\u003efilter wheels\u003c\/a\u003e that take unmounted filters. The sizing below is typical and depends on filter-to-sensor spacing and focal ratio.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" and 31 mm:\u003c\/strong\u003e Typically used with smaller sensors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm:\u003c\/strong\u003e Typically used for APS-C class sensors in a filter wheel.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2\", 50 mm Round, and 50x50 mm Square:\u003c\/strong\u003e Typically needed for full-frame (36 x 24 mm) sensors.\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 Chroma R-Bessell filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Chroma R-Bessell filter is a scientific tool for \u003cstrong\u003ephotometry\u003c\/strong\u003e, the precise measurement of the brightness of celestial objects. It isolates a standardized red band of light defined by the Bessell UBVRI system, allowing astronomers to collect data that can be compared with results from other observers and professional institutions worldwide.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Chroma R-Bessell filter for general deep-sky imaging?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile you can take an image with it, it is not ideal for creating full-color (LRGB) portraits of nebulae or galaxies. Its bandpass is designed for scientific measurement, not for matching human color perception. For aesthetic astrophotography, a dedicated \u003ca href=\"\/en-us\/collections\/lrgb-filters\"\u003eLRGB filter set\u003c\/a\u003e is the better choice.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does \"parfocal\" mean for the Chroma R-Bessell filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eChroma astronomy filters (except LoGlow) are made on the same 3.0 mm thick substrate and are parfocal, so switching from the R-Bessell to a V-Bessell or B-Bessell filter in the same wheel does not shift focus because of the filter itself; any remaining difference comes from your telescope's color correction. This is critical for automated imaging sequences and saves significant time during an observing session.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would I use the Chroma R-Bessell filter to measure the light curve of a variable star like Algol (Beta Persei)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eTo measure Algol's light curve, you would take a series of timed exposures through the Chroma R-Bessell filter, along with exposures of nearby, non-variable comparison stars in the same field. Using photometry software, you measure the instrumental magnitude of Algol relative to the stable comparison stars in each image. Plotting these relative magnitudes over time reveals the star's periodic dimming as its companion eclipses it.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the difference between this Chroma R-Bessell filter and a standard \"Red\" filter from an LRGB set?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA standard LRGB \"Red\" filter is designed to create a visually pleasing color image by capturing a broad swath of the red spectrum. The \u003cstrong\u003eChroma R-Bessell filter\u003c\/strong\u003e has a more specific, standardized bandpass defined for scientific photometry. While they both pass red light, the Bessell filter's profile is engineered for repeatable, scientific measurement, not aesthetic color balance.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhich size Chroma R-Bessell filter do I need for my full-frame camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eFor a full-frame sensor (e.g., 36x24 mm), you should choose either the \u003cstrong\u003e2\" mounted\u003c\/strong\u003e, \u003cstrong\u003e50 mm round unmounted\u003c\/strong\u003e, or \u003cstrong\u003e50x50 mm square unmounted\u003c\/strong\u003e filter. Smaller sizes like 36 mm or 1.25\" will likely cause significant vignetting (darkening of the corners) on a full-frame sensor.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI have a fast f\/4 telescope. Will the Chroma R-Bessell filter work correctly?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Bessell photometric filters carry no focal-ratio rating; the f\/4.0-or-slower design note applies to Chroma's imaging filters. As a broadband filter, the R-Bessell is far less sensitive to focal-ratio shift than a \u003ca href=\"\/en-us\/collections\/narrowband-filters\"\u003enarrowband filter\u003c\/a\u003e, but for precise photometry, calibrate with standard stars through your own optical system.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Chroma R-Bessell filter covered by a warranty?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. All Chroma sputtered catalog filters are protected by a \u003cstrong\u003elifetime warranty\u003c\/strong\u003e against defect under normal use. All Chroma catalog filters also carry a one-year full satisfaction warranty.\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\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eChroma Technology Corp\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePart Number\u003c\/td\u003e\n\u003ctd\u003e27053\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCountry of Manufacture\u003c\/td\u003e\n\u003ctd\u003eVermont, USA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Substrate Thickness\u003c\/td\u003e\n\u003ctd\u003e3.0 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eParfocal\u003c\/td\u003e\n\u003ctd\u003eYes, with other Chroma astronomy filters (except LoGlow 27030)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmitted Wavefront\u003c\/td\u003e\n\u003ctd\u003eBetter than 0.25 waves\/inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eDurable sputtered hard coatings on a single substrate, AR coating on rear\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" mounted, 2\" mounted, 31 mm unmounted, 36 mm unmounted, 50 mm unmounted, 50x50 mm unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCell Thread (Mounted)\u003c\/td\u003e\n\u003ctd\u003e1.25\": M28.5x0.6 male; 2\": M48x0.75 male\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWarranty\u003c\/td\u003e\n\u003ctd\u003eChroma Lifetime Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Thickness\u003c\/td\u003e\n\u003ctd\u003e3 mm\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\"\u003eChroma R-Bessell 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\u003ca href=\"https:\/\/www.chroma.com\/resources\/customer-support\/warranty-information\/\" rel=\"noopener\" target=\"_blank\"\u003eChroma Technology Lifetime Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Chroma","offers":[{"title":"1.25\" Round Mounted","offer_id":44967249740061,"sku":"CT-27053-1.25M","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967249772829,"sku":"CT-27053-31D","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967249805597,"sku":"CT-27053-36D","price":483.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967249838365,"sku":"CT-27053-2M","price":980.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967249871133,"sku":"CT-27053-50D","price":910.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967249903901,"sku":"CT-27053-50X50","price":1015.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Transmission-Curve-of-Chroma-R-Bessel-Filter__30129.1596071526.1280.1280.jpg?v=1684339726"},{"product_id":"chroma-i-bessel-filter","title":"Chroma I-Bessell Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eStandard I-Bessell filter for scientific photometry\u003c\/li\u003e\n\u003cli\u003eDurable sputtered hard coatings on a single substrate\u003c\/li\u003e\n\u003cli\u003e3.0 mm substrate, parfocal with other Chroma astronomy filters (except LoGlow)\u003c\/li\u003e\n\u003cli\u003eTransmitted wavefront better than 0.25 waves\/inch\u003c\/li\u003e\n\u003cli\u003eAnti-reflection coating on rear surface to prevent ghosting\u003c\/li\u003e\n\u003cli\u003eMade in Vermont, USA with a lifetime warranty\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\u003eChroma I-Bessell Filter\u003c\/h2\u003e\n\u003cp\u003eThe Chroma I-Bessell Filter is a scientific-grade photometric tool built on a 3.0 mm thick substrate with a transmitted wavefront better than 0.25 waves\/inch. This filter isolates the near-infrared I-band of the standard Johnson-Cousins\/Bessell UBVRI system, enabling precise stellar magnitude measurements. Each filter features durable sputtered hard coatings on a single substrate for high transmission and durability, backed by Chroma's lifetime warranty.\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 I-Bessell Standard: Scientific Photometry, Better Than 0.25 Waves\/Inch\u003c\/h3\u003e\n\u003cp\u003eThis is not an aesthetic imaging filter; it is a precision instrument for data acquisition. The I-Bessell filter isolates the near-infrared portion of the spectrum, a critical band for determining the temperature and classification of cooler stars. Because it matches the Bessell realization of the Johnson-Cousins system, your measurements can be compared with standard UBVRI data, which makes it useful for variable star monitoring, exoplanet transit light curves and stellar photometry.\u003c\/p\u003e\n\u003cp\u003eIts transmitted wavefront is better than 0.25 waves\/inch, so it adds very little wavefront error to your imaging train.\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\u003eProfessional-Grade Build: A 3.0 mm Parfocal Construction\u003c\/h3\u003e\n\u003cp\u003eChroma's astronomy filters are built in Vermont, USA. The I-Bessell is built on a single 3.0 mm thick glass substrate with no laminations. This thickness makes it parfocal with other Chroma astronomy filters (except LoGlow), so you can switch between U, B, V, R, and I bands without significant refocusing, saving critical time during an observing run.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSputtered Hard Coatings:\u003c\/strong\u003e Chroma tests its sputtered hard coatings for abrasion, humidity and temperature exposure.\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAnti-Reflection Treatment:\u003c\/strong\u003e The rear surface is treated with an anti-reflection coating to prevent ghosting and maximize transmission.\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSingle Substrate:\u003c\/strong\u003e Each filter is a single substrate with no laminations.\n\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\u003eSizing for Modern Sensors: From 1.25\" to 50x50 mm\u003c\/h3\u003e\n\u003cp\u003eChroma offers the I-Bessell filter in six sizes. Choosing the correct size is critical for flat-fielding and accurate photometry across your entire image. The mounted versions include standard M28.5x0.6 male threads for 1.25\" cells and M48x0.75 male threads for 2\" \u003ca href=\"\/en-us\/collections\/filter-wheels\"\u003efilter wheels\u003c\/a\u003e.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" Mounted \u0026amp; 31 mm Unmounted:\u003c\/strong\u003e Typically suit smaller sensors or filter wheels with a smaller clear aperture.\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2\" Mounted \u0026amp; 36 mm Unmounted:\u003c\/strong\u003e Typically cover sensors up to APS-C class.\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e50 mm Round \u0026amp; 50x50 mm Square:\u003c\/strong\u003e Typically chosen for full-frame (36 x 24 mm) class sensors.\n\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 Chroma I-Bessell filter used for in astronomy?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003eChroma I-Bessell filter\u003c\/strong\u003e is a scientific photometric filter designed for precise measurement of celestial object brightness in the near-infrared spectrum. It is a core component of the UBVRI system used to classify stars, measure their temperature, and record light curves of variable stars and exoplanet transits. It is a tool for data collection, not for creating color images.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Chroma I-Bessell filter parfocal with my other Chroma filters?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The Chroma I-Bessell filter is manufactured on a \u003cstrong\u003e3.0 mm thick substrate\u003c\/strong\u003e, making it parfocal with other Chroma astronomy filters (with the exception of the LoGlow filter). This means you can switch between your Chroma LRGB, narrowband, and photometric filters without needing to make major focus adjustments.\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 I-Bessell filter for my camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe correct filter size depends on your camera's sensor size and your telescope's focal ratio. As a general guide:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e31 mm \/ 1.25\" mounted:\u003c\/strong\u003e Typically for smaller sensors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm \/ 2\" mounted:\u003c\/strong\u003e Typically cover sensors up to APS-C class.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e50 mm round or 50x50 mm square:\u003c\/strong\u003e Typically chosen for full-frame class sensors.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would the Chroma I-Bessell filter help measure an exoplanet transit with my monochrome camera and 11\" SCT?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhen an exoplanet transits its star, it causes a tiny dip in the star's brightness. The I-Bessell filter can help here because cool red dwarf stars, the most common type, emit strongly in the near-infrared. For such a star, the \u003cstrong\u003eChroma I-Bessell filter\u003c\/strong\u003e collects more of its light, improving the signal-to-noise ratio of your light curve and making the small dip in brightness easier to detect and measure accurately.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI'm classifying stars in the Hercules Cluster (M13). How does the I-Bessell filter contribute?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eTo classify stars, you need to measure their color index, the difference in brightness through different filters. By taking images of M13 through the B-Bessell (blue) and V-Bessell (visual) filters, and then the \u003cstrong\u003eI-Bessell filter\u003c\/strong\u003e, you can measure the B-V and V-I color indices. These values are critical for placing stars on a Hertzsprung-Russell diagram, which reveals their temperature, age, and evolutionary stage. The I-band is especially important for accurately plotting the temperatures of the cooler red giant stars in the cluster.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy do Chroma's sputtered coatings matter for a photometric filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eChroma uses \u003cstrong\u003edurable sputtered hard coatings\u003c\/strong\u003e. Chroma engineers these hard-sputtered coatings for durability and spectral stability across temperature changes, humidity and years of use. For photometry, this means the filter's transmission profile remains stable for years, ensuring your measurements are consistent and repeatable, which is essential for long-term scientific projects.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the Chroma I-Bessell filter have a lifetime warranty?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. All Chroma sputtered catalog filters, including the \u003cstrong\u003eI-Bessell filter\u003c\/strong\u003e, are covered by a lifetime warranty against defect under normal use. They are made in Vermont, USA.\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\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eChroma Technology Corp\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePart Number\u003c\/td\u003e\n\u003ctd\u003e27054\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003eBessell I-Band Photometric\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" mounted, 2\" mounted, 31 mm unmounted, 36 mm unmounted, 50 mm unmounted, 50x50 mm unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCell Threads\u003c\/td\u003e\n\u003ctd\u003e1.25\": M28.5x0.6 (male); 2\": M48x0.75 (male)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Substrate Thickness\u003c\/td\u003e\n\u003ctd\u003e3.0 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eParfocal\u003c\/td\u003e\n\u003ctd\u003eYes, with other Chroma astronomy filters\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmitted Wavefront\u003c\/td\u003e\n\u003ctd\u003eBetter than 0.25 waves\/inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eDurable sputtered hard coatings\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAnti-Reflection Coating\u003c\/td\u003e\n\u003ctd\u003eYes, on rear surface\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCountry of Origin\u003c\/td\u003e\n\u003ctd\u003eUSA (Vermont)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWarranty\u003c\/td\u003e\n\u003ctd\u003eChroma Lifetime Warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Thickness\u003c\/td\u003e\n\u003ctd\u003e3 mm\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\"\u003eChroma I-Bessell 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\u003ca href=\"https:\/\/www.chroma.com\/resources\/customer-support\/warranty-information\/\" rel=\"noopener\" target=\"_blank\"\u003eChroma Technology Lifetime Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Chroma","offers":[{"title":"1.25\" Round Mounted","offer_id":44967250034973,"sku":"CT-27054-1.25M","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967250067741,"sku":"CT-27054-31D","price":385.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967250100509,"sku":"CT-27054-36D","price":483.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967250133277,"sku":"CT-27054-2M","price":980.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967250166045,"sku":"CT-27054-50D","price":910.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967250198813,"sku":"CT-27054-50X50","price":1015.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Transmission-Curve-of-Chroma-I-Bessel-Filter__54362.1596071527.1280.1280.jpg?v=1684339728"},{"product_id":"chroma-ubvri-filter-set","title":"Chroma UBVRI Filter Set","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eComplete 5-filter Bessell UBVRI photometric set (Johnson-Cousins system)\u003c\/li\u003e\n\u003cli\u003e3.0 mm thick substrates, parfocal with other Chroma astronomy filters (except LoGlow)\u003c\/li\u003e\n\u003cli\u003eDurable, high-transmission sputtered hard coatings\u003c\/li\u003e\n\u003cli\u003eTransmitted wavefront better than 0.25 waves\/inch\u003c\/li\u003e\n\n\u003cli\u003eMade in Vermont, USA with a lifetime warranty\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\u003eChroma UBVRI Filter Set\u003c\/h2\u003e\n\u003cp\u003eThe Chroma UBVRI Filter Set provides a complete, research-grade solution for scientific photometry based on the Bessell realization of the Johnson-Cousins system, with each filter built on a solid 3.0 mm glass substrate. This set is engineered for precision measurement, featuring a transmitted wavefront better than 0.25 waves\/inch. Manufactured in Vermont, USA, these filters use durable sputtered hard coatings on a single substrate with high transmission, and are parfocal across the set and with other Chroma astronomy filters (except LoGlow), so the filters themselves do not shift focus between bands.\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 UBVRI System for Scientific Imaging\u003c\/h3\u003e\n\u003cp\u003eThis is not an LRGB set for creating pretty pictures; it is a scientific instrument for measuring the brightness and color of celestial objects. The UBVRI system is a widely used standard system for photometry, allowing your data to be compared with professional observations worldwide. Each filter isolates a specific passband for quantifying stellar magnitudes.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eU (Ultraviolet):\u003c\/strong\u003e Captures the near-UV, crucial for characterizing hot, young O- and B-type stars and active galactic nuclei.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eB (Blue):\u003c\/strong\u003e Isolates the blue portion of the spectrum, forming the blue-end baseline for color index calculations.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eV (Visual):\u003c\/strong\u003e Centered in the green, this band closely matches the peak sensitivity of the human eye and serves as the standard for visual magnitude.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eR (Red):\u003c\/strong\u003e Covers the red part of the visible spectrum, essential for studying cooler stars like K and M-types.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eI (Infrared):\u003c\/strong\u003e Samples the near-infrared, providing critical data on the coolest red dwarf stars and heavily reddened objects.\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\u003e3.0mm Parfocal Substrates and 0.25 Waves\/Inch Wavefront\u003c\/h3\u003e\n\u003cp\u003eEach filter in the UBVRI set is manufactured on a single 3.0 mm thick substrate, ensuring they are parfocal. The filters themselves do not shift focus between bands, though your telescope's color correction can leave small focus differences between the U and I ends. Transmitted wavefront is better than 0.25 waves\/inch.\u003c\/p\u003e\n\u003cp\u003eThe coatings are applied by reactive magnetron sputtering on a single substrate with no laminations; they withstand humidity changes and extreme temperature fluxes, while anti-reflection coatings on the rear surface prevent ghosting and internal reflections from bright stars.\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\u003eFocal Ratio and Photometric Accuracy\u003c\/h3\u003e\n\u003cp\u003eThe Bessell photometric filters carry no focal-ratio rating. All interference filters experience a \"blue shift\" in their passband when used in the converging light cone of a fast telescope; broadband photometric filters are far less sensitive to this than \u003ca href=\"\/en-us\/collections\/narrowband-filters\"\u003enarrowband filters\u003c\/a\u003e, but the shift grows as the focal ratio gets faster.\u003c\/p\u003e\n\u003cp\u003eFor precise photometry, calibrate with standard stars through your own optical system, which accounts for your telescope, filters and camera together.\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\u003eUBVRI vs. LRGB: When to Choose a Photometric Filter Set\u003c\/h3\u003e\n\u003cp\u003eThe choice between a UBVRI set and a standard LRGB (Luminance, Red, Green, Blue) set comes down to your primary goal: data or aesthetics. \u003ca href=\"\/en-us\/collections\/lrgb-filters\"\u003eLRGB filters\u003c\/a\u003e are designed for color rendering, and their passbands are not standardized for measurement.\u003c\/p\u003e\n\u003cp\u003eThe Chroma UBVRI set, in contrast, is matched to the Bessell realization of the Johnson-Cousins system, whose broad passbands are defined for measurement. This allows you to produce light curves of a variable star or determine the color index of an asteroid with data that, after standard calibration, is comparable with professional research. While you can combine UBVRI data to create a color image, its purpose is analysis, not just presentation.\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 purpose of the Chroma UBVRI Filter Set?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Chroma UBVRI set is designed for scientific astrophotography, specifically \u003cstrong\u003ephotometry\u003c\/strong\u003e. Its purpose is to accurately measure the brightness of celestial objects like variable stars, asteroids, and supernovae in the standardized Johnson-Cousins UBVRI passbands, allowing your data to be compared with professional observations.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Chroma UBVRI set for creating color images like an LRGB set?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile you can create color images by mapping the B, V, and R filters to blue, green, and red, the result will differ from a standard LRGB image. The UBVRI passbands are designed for scientific measurement, not for mimicking human color vision. An LRGB filter set is the better choice if your main goal is visually appealing color astrophotography.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the Chroma UBVRI filters work with an f\/2 telescope?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eOnly with care. The Bessell photometric filters carry no focal-ratio rating, but in an f\/2 system the steep light cone shifts every interference filter's passband toward the blue, moving it away from the standard Johnson-Cousins response. Calibrate with standard stars through your own system before relying on the data.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI want to measure the variability of the eclipsing binary Algol (Beta Persei). Is the Chroma UBVRI set suitable?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. Eclipsing binaries are a classic photometry target. By taking a time-series of exposures through the V-band filter, you can create a precise light curve showing Algol's brightness changes. Comparing measurements through the B and V filters allows you to track color index changes during the eclipse, providing deeper physical insight into the star system.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eAre all the filters in the Chroma UBVRI set parfocal?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. All filters in this set are manufactured on \u003cstrong\u003e3.0 mm thick substrates\u003c\/strong\u003e, so they are parfocal with each other and with other Chroma astronomy filters (except LoGlow). The filters themselves do not shift focus when you switch between U, B, V, R and I, though your telescope's color correction can still leave small focus differences between the U and I ends.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does a transmitted wavefront of \"better than 0.25 waves\/inch\" mean for the Chroma UBVRI filters?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIt means less than a quarter wave of wavefront error per inch of filter, which helps the filter keep the sharpness your telescope delivers.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat size Chroma UBVRI filter do I need for my camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe correct size depends on your camera sensor's \u003ca href=\"\/en-us\/collections\/diagonals\"\u003ediagonal\u003c\/a\u003e and the focal ratio of your telescope. As a general guide:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" or 31 mm:\u003c\/strong\u003e Typically suit sensors up to about 16mm diagonal.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm:\u003c\/strong\u003e Typically used for APS-C class sensors (about 28mm diagonal).\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2\" or 50 mm:\u003c\/strong\u003e Typically needed for full-frame sensors (about 43mm diagonal) to avoid vignetting.\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\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eChroma Technology Corp (Vermont, USA)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003eBessell UBVRI Photometric Set\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChroma Part Number\u003c\/td\u003e\n\u003ctd\u003e27103\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Thickness\u003c\/td\u003e\n\u003ctd\u003e3.0 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eParfocal\u003c\/td\u003e\n\u003ctd\u003eYes, with other 3.0 mm Chroma astronomy filters\u003c\/td\u003e\n\u003c\/tr\u003e\n\n\u003ctr\u003e\n\u003ctd\u003eTransmitted Wavefront\u003c\/td\u003e\n\u003ctd\u003eBetter than 0.25 waves\/inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eDurable sputtered hard coatings\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAnti-Reflection\u003c\/td\u003e\n\u003ctd\u003eYes, on rear surface\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSubstrate\u003c\/td\u003e\n\u003ctd\u003eSingle, non-laminated\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSizes Offered\u003c\/td\u003e\n\u003ctd\u003e1.25\" mounted, 2\" mounted, 31mm unmounted, 36mm unmounted, 50mm unmounted, 50x50mm square\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCell Thread (Mounted)\u003c\/td\u003e\n\u003ctd\u003e1.25\": M28.5x0.6 male; 2\": M48x0.75 male\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCountry of Origin\u003c\/td\u003e\n\u003ctd\u003eMade in Vermont, USA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWarranty\u003c\/td\u003e\n\u003ctd\u003eChroma Lifetime Warranty\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\"\u003eChroma 27050 U-Bessell filter\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\"\u003eChroma 27052 B-Bessell filter\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\"\u003eChroma 27051 V-Bessell filter\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\"\u003eChroma 27053 R-Bessell filter\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\"\u003eChroma 27054 I-Bessell 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\u003ca href=\"https:\/\/www.chroma.com\/resources\/customer-support\/warranty-information\/\" rel=\"noopener\" target=\"_blank\"\u003eChroma Technology Lifetime Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Chroma","offers":[{"title":"1.25\" Round Mounted","offer_id":44967250264349,"sku":"CT-27103-1.25M","price":1645.0,"currency_code":"CAD","in_stock":true},{"title":"31mm Round Unmounted","offer_id":44967250297117,"sku":"CT-27103-31D","price":2275.0,"currency_code":"CAD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":44967250329885,"sku":"CT-27103-36D","price":2415.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Round Mounted","offer_id":44967250362653,"sku":"CT-27103-2M","price":4620.0,"currency_code":"CAD","in_stock":true},{"title":"50mm Round Unmounted","offer_id":44967250395421,"sku":"CT-27103-50D","price":4270.0,"currency_code":"CAD","in_stock":true},{"title":"50x50mm Square Unmounted","offer_id":44967250428189,"sku":"CT-27103-50X50","price":4795.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/Transmission-Curve-of-Chroma-Bessel-UBVRI-Filters__13320.1596071528.1280.1280.jpg?v=1684339731"}],"url":"https:\/\/davidastro.com\/en-us\/collections\/chroma-bessel-ubvri-photometric-filters.oembed","provider":"David Astro","version":"1.0","type":"link"}