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All Chroma 31mm H-alpha 3nm Telescope Filter
Chroma 31mm H-alpha 3nm Telescope Filter

Chroma 31mm H-alpha 3nm Telescope Filter

SKU : CF-HA3-31

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$575

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  • 31mm H-alpha 3nm Narrowband Filter
  • Parfocal for systems f/4.0 or slower
  • Transmitted wavefront better than 0.25 waves/inch
  • Made in America
  • Filter sizes up to 2-inch & 50mm Square come with a complimentary TPO Filter Case (OS-CF2) to keep your filter safe.

Product Details

  • Please Note:The interference coatings that optical filters are made with are angle-sensitive and shift to the blue with fast focal ratios. This is not a problem for filters 5nm or wider, but the 3nm filters shift enough to compromise transmission at the wavelength line of interest. Chroma has made a set of Ha, OIII and SII 3nm that are optimized for F/3 beams by moving the center wavelength slightly into the red so they will shift slightly to the blue when used in an F/3 beam, thus maximizing transmission at the nominal wavelength. For beams faster than F/3, we recommend using 5nm-wide or wider bands.

    The Chroma 31mm H-alpha 3nm Narrowband Filter is essential for imaging objects, like nebulae, that are rich in ionized hydrogen atoms. These line emission filters work extremely well in heavy light polluted areas and allow you image on nights when the moon is up.

    Chroma manufactures the highest quality astronomy filters with durable, sputtered hard coating using single substrates of the best glass, eliminating the need for laminations. All primary filter coatings are applied on the front surface and anti-reflection coatings on the rear surface to prevent ghosting and to maximize transmission.

    Highly precise and accurate, the passbands of these filters remain spectrally stable and do not drift in response to extreme temperature fluctuations or changes in humidity.

  • specifications

    Bandpass3nm
    Filter ShapeRound
    Filter Thickness1mm
    Filter TypeH Alpha
    Free ShippingYes
    Size31mm

  • included items

    • 31mm H-alpha 3nm Narrowband Filter
    • Parfocal for systems f/4.0 or slower
    • Transmitted wavefront better than 0.25 waves/inch
    • Made in America
    • Filter sizes up to 2-inch & 50mm Square come with a complimentary TPO Filter Case (OS-CF2) to keep your filter safe.

Product Reviews

Customer Reviews
4.0 Based on 2 Reviews
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Filter Reviews:
    J
    03/03/2021
    Jose
    United States United States

    Works great@

    This 3nm Sii filter is a significant improvement over my previous 7nm filter. Some have complained of uneven flats but keep in mind that cmos sensors have the problem, not the filter, and it all gets eliminated with flats. You can find lengthy forum discussions on this issue. My imaging has greatly improved with this filter and no more halos!

    OPT Telescopes Chroma 31mm H-alpha 3nm Telescope Filter Review
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    TZ
    04/23/2020
    Theresa Z.
    United States United States

    Not sure whether these are good or not yet

    I have done some flat processing and getting really strange results, so not quite sure what is going on. Haven’t had time to follow-up with Chroma or OPT yet.

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