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Chroma V-Bessell Filter

Chroma V-Bessell Filter

by Chroma
SKU CT-27051-1.25M
CA$385.00 - CA$1,015.00
CA$385.00
CA$385.00 - CA$1,015.00
CA$385.00
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  • Standard V-Bessell photometric filter for scientific measurement
  • 3.0 mm thick substrate ensures parfocality with other Chroma filters
  • Transmitted wavefront better than 0.25 waves/inch
  • Durable, sputtered hard coatings with anti-reflection on the rear surface
  • Available in 1.25" and 2" mounted, and 31mm, 36mm, 50mm, and 50x50mm unmounted formats
  • Made in Vermont, USA with a lifetime warranty
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Chroma V-Bessell Filter

    The 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.

    The V-Bessell Band: A Standard for Scientific Photometry

    This 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.

    Built for Data Integrity: 3.0mm Parfocal Substrate & Better Than 0.25 Waves/Inch Wavefront

    The 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.

    • Sputtered Hard Coatings: Chroma's sputtered coatings are deposited on a single glass substrate and are built to withstand humidity changes and extreme temperature fluxes.
    • Anti-Reflection Treatment: The rear surface is anti-reflection coated to prevent ghosting and internal reflections, which can corrupt photometric measurements and contaminate faint targets.

    Choosing Your Format: From 1.25" to 50mm Square

    The 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 filter wheels 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.

  • What is the Chroma V-Bessell filter primarily used for?

    The Chroma V-Bessell filter is designed for scientific photometry. 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.

    Is the Chroma V-Bessell filter the same as a regular "Green" LRGB filter?

    No. While both pass green light, they have different purposes. The V-Bessell filter has a strictly defined bandpass for scientific measurement. A standard LRGB Green filter is designed for aesthetic color balance in astrophotography and has a different transmission curve, which makes it unsuitable for standard photometry.

    How would I use the Chroma V-Bessell filter to measure a variable star like Algol (Beta Persei)?

    You 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.

    Will the 36mm unmounted Chroma V-Bessell filter work with my APS-C camera?

    Typically, 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.

    Why is the 3.0mm thickness of the Chroma V-Bessell filter important?

    The uniform 3.0 mm thickness makes the filter parfocal 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.

    Do I need the other U, B, R, and I filters to use the Chroma V-Bessell?

    While 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.

  • Manufacturer Chroma Technology Corp
    Part Number 27051
    Filter Type Photometric (V-Bessell)
    Available Formats 1.25" mounted (M28.5x0.6), 2" mounted (M48x0.75), 31mm unmounted, 36mm unmounted, 50mm unmounted, 50x50mm square
    Glass Thickness 3.0 mm
    Parfocal Yes, with other Chroma astronomy filters
    Coatings Durable sputtered hard coatings, AR-coated rear surface
    Transmitted Wavefront Better than 0.25 waves/inch
    Country of Origin Vermont, USA
    Warranty Chroma Lifetime Warranty

    • Chroma V-Bessell Filter

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  • Chroma Lifetime Warranty