Skip to content
Price match 30-day returns* Talk to an astronomer before you buy
Chroma Luminance Filter

Chroma Luminance Filter

by Chroma
SKU CT-27040-1.25M
CA$210.00 - CA$700.00
CA$210.00
CA$210.00 - CA$700.00
CA$210.00
Price Match Policy!
  • Captures the full visible spectrum for high-resolution LRGB imaging
  • 3.0 mm substrate, parfocal with other Chroma astronomy filters (except LoGlow)
  • Transmitted wavefront better than 0.25 waves/inch
  • Designed for optical systems of f/4.0 or slower
  • Durable sputtered hard coatings on a single substrate
  • Made in Vermont, USA, and backed by a lifetime warranty
Backordered
Request Stock Alert
Availability Info
Qualifies for FREE Shipping in Canada on orders over $500.
Vignetting Calculator

Will your imaging train vignette?

Check which filter and adapter sizes clear the sensor with the Chroma Luminance Filter, and how much light the corners lose.

Check vignetting
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Chroma Luminance Filter

    The Chroma Luminance Filter is the foundation of high-resolution LRGB astrophotography, built on a 3.0 mm substrate and parfocal with Chroma's other astronomy filters (except LoGlow). Its durable sputtered coatings pass the visible spectrum, and its transmitted wavefront is better than 0.25 waves/inch. Designed for systems at f/4.0 and slower, this filter allows you to spend the majority of your imaging time gathering deep structural data, which can then be combined with shorter color exposures for a final image with better signal-to-noise.

    Better than 0.25 Waves/Inch Wavefront for LRGB Detail

    In an LRGB imaging workflow, the Luminance channel is responsible for nearly all of the final image's sharpness, contrast, and fine detail. The Chroma Luminance Filter is designed to transmit the full visible spectrum, allowing your monochrome camera to record more signal per exposure than any single color filter. This high-throughput signal becomes the high-resolution backbone of your image, onto which color data from RGB filters is layered.

    Chroma specifies a transmitted wavefront better than 0.25 waves/inch for this filter. The result is a deeply detailed monochrome image that forms a pristine canvas for color, revealing faint galactic dust lanes and fine structures that would be lost in shorter RGB-only exposures.

    3.0mm Parfocal Design with Sputtered Coatings

    Chroma's astronomy filters are built on 3.0 mm glass substrates and are parfocal with one another. This parfocal design is critical for automated imaging, eliminating the need to refocus your telescope when the filter wheel switches between this Luminance filter and your Chroma RGB or narrowband filters. The only exception is the LoGlow filter, which uses a different substrate thickness.

    • Sputtered Hard Coatings: The coatings are applied using a reactive magnetron sputtering process. The result is a durable coating on a single substrate with no laminations; Chroma states its coatings withstand humidity changes and extreme temperature fluxes and remain spectrally accurate.
    • Anti-Reflection Treatment: The primary filter coating is on the front surface, while the rear surface receives an anti-reflection coating. This design prevents ghosting and internal reflections from bright stars, preserving image contrast.
    • Made in the USA: Each filter is manufactured at Chroma's facility in Vermont, USA, and is covered by Chroma's lifetime warranty against defect under normal use.

    Sizing for Your Sensor and f/4.0+ Optics

    Chroma designs the Luminance filter for f/4.0 or slower.

    Choosing the correct filter size is essential to avoid vignetting. Chroma offers six sizes. The guidance below is typical; actual coverage depends on filter-to-sensor spacing and focal ratio:

    • 1.25" and 31mm: Typically used with smaller sensors: roughly up to a 16mm diagonal for 1.25", and up to about the Four Thirds class for 31mm.
    • 36mm: Typically used for APS-C class sensors in a filter wheel.
    • 2", 50mm Round, and 50x50mm Square: Typically needed for full-frame (36x24mm) sensors to illuminate the sensor to the corners.

  • What is the main advantage of using the Chroma Luminance filter in an LRGB workflow?

    The Chroma Luminance filter captures the entire visible spectrum with high transmission, allowing you to gather a deep, high-resolution monochrome image much faster than you could with separate RGB filters. This high-signal "L" layer provides all the detail and contrast for the final image, while shorter exposures through RGB filters are used only to add color. The result is a much higher signal-to-noise ratio than a simple RGB composite.

    Is the Chroma Luminance filter parfocal with other Chroma filters?

    Yes. All Chroma astronomy filters, including this Luminance filter, are manufactured on a 3.0 mm thick substrate, making them parfocal. This means you can switch between your L, R, G, B, and narrowband Chroma filters without having to adjust your focuser. The only exception noted by Chroma is their LoGlow Light Pollution Filter (part #27030).

    Which size Chroma Luminance filter do I need for an APS-C or full-frame sensor?

    To avoid vignetting (darkening of the corners of your image), you should match the filter size to your sensor. For most APS-C sensors (around 28mm diagonal), the 36mm unmounted filter is the typical choice. For full-frame sensors (43mm diagonal), you will typically need a 2" mounted, 50mm round, or 50x50mm square filter to fully illuminate the sensor.

    How will the Chroma Luminance filter perform on my f/8 refractor when imaging the Andromeda Galaxy (M31)?

    An f/8 refractor is within the filter's design range of f/4.0 or slower. When imaging a broad-spectrum target like the Andromeda Galaxy (M31), the filter records the galaxy's core, dust lanes and faint outer arms as the detail layer for your LRGB image.

    Can I use the Chroma Luminance filter on an f/2 system?

    The Chroma Luminance filter is specified for systems of f/4.0 or slower. While you can use it on a faster f/2 system, the extremely steep light cone can cause a slight shift in the filter's bandpass. For a broadband filter like Luminance, this effect is generally minimal compared to a narrowband filter, but it is outside the manufacturer's specified design range.

    What does the "transmitted wavefront better than 0.25 waves/inch" specification mean for my images?

    It describes how much the filter distorts the light passing through it: less than a quarter wave of wavefront error per inch of filter. A low transmitted wavefront error helps the filter keep the sharpness your telescope delivers.

    Where is the Chroma Luminance filter made and what is its warranty?

    All Chroma astronomy filters are manufactured in Vermont, USA. They are covered by the Chroma lifetime warranty for sputtered catalog filters, which covers defects under normal use. All Chroma catalog filters also carry a one-year full satisfaction warranty.

  • Manufacturer Chroma Technology Corp
    Part Number 27040
    Country of Origin Vermont, USA
    Substrate Thickness 3.0 mm
    Parfocal Yes, with all other 3.0mm Chroma astronomy filters
    Transmitted Wavefront Better than 0.25 waves/inch
    Recommended Focal Ratio f/4.0 or slower
    Coatings Durable sputtered hard coatings
    Anti-Reflection Yes, on rear surface
    Sizes Offered 1.25" mounted, 2" mounted, 31mm unmounted, 36mm unmounted, 50mm unmounted, 50x50mm unmounted
    Cell Thread (Mounted) 1.25": M28.5x0.6 male; 2": M48x0.75 male
    Warranty Chroma Lifetime Warranty

    • Chroma Luminance Filter

      × 1

  • Chroma Technology Lifetime Warranty