Optolong H-Alpha 7nm CCD Filter - 31mm Unmounted - HAL7-31U

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Item #OLNG-HAL7-31U

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  • The Hydrogen-Alpha 7nm filter by Optolong is a highly narrow emission-line filter
  • Transmits a 7nm bandwidth of light, centered on the 656nm wavelength
  • Also blocks contrast-killing light pollution wavelengths
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  • Description

    Optolong H-Alpha CCD 7nm Filter - 31mm  Unmounted

    The Optolong H-Alpha 7nm is an exceptionally narrow emission-line filter and measures 31mm in diameter. The H-Alpha filter enables a 7nm bandwidth of light from the 56nm wavelength, to pass through. The filter also blocks transmission of contrast-killing light pollution wavelengths. The wavelengths notorious for natural light pollution, or skyglow are nearly eliminated. This is also true for artificial light pollution caused by high and low-pressure sodium vapor as well as mercury vapor lights. The result is a high contrast image that reveals the H-alpha line in all its glory.

    This Optolong H-Alpha filter will provide the ultimate in contrast between the skyglow background and H-alpha emitting objects, but because it has a FWHM of just 7nm, you won’t see as many stars in the final image as you would with the Optolong 12nm H-Alpha Filter. Use this filter alone for CCD or DSLR imaging, or use together with OIII 6.5nm and SII 6.5nm filters to get a tricolor image of the gaseous nebula from light polluted skies. Like all Optolong filters that are designated as “CCD”, this H-Alpha filter also blocks infrared wavelengths from 700nm to 1100nm so you don't need a separate IR-Cut filter.

    The Optolong 31mm Unmounted H-Alpha 7nm Filter is made with Schott glass that has been multi-coated with an ion-assisted deposition technology to ensure scratch resistance and stability on the central wavelength, or CWL. This ultra narrowband 7nm H-alpha filter is designed to be used in color filter wheels that accept 31mm unmounted filters in a round format.

    Please Note: This h-alpha filter is NOT for use on the Sun. To do so could cause irreparable eye damage or blindness. Don’t even think about it!


    Quality Filter Materials:

    • Schott B260 substrate material from Germany, 2.0mm thick
    • Multiple layers of anti-reflection non-cementing coatings applied via electron-beam gun evaporation with Ion-assisted deposition


    Optolong Filter Manufacturing Processes and Parameters

    • Filter substrate is fine-optically polished to 1/4 wave and <30 parallelism over both surfaces
    • Surface quality, according to MIL-O-13830, is 60/40
    • 80% transmission at H-alpha 656nm
    • Infrared wavelength of 700-1100nm is cut off
    • 0.1% transmission Hg at 435nm and 578nm
    • 0.1% transmission Na at 589nm
    • High-value transmission of pass-band and optical density of off-band is assured through Optolong’s planetary rotation system, a homogeneous and precise coating procedure
    • Each filter comes with a plastic case with high-pressure EVA case lining


    About Optolong

    Optolong is the Astronomy Filters division of Yulong Optics, an optical filter design and processing company out of Kunming, China that has provided filters for over 700 optical companies since 1999. All Optolong filters pass European Union RoHS requirements and have been certified by TUV Rheinland and Bureau Veritas. 


    Supplier SKU


    What's Included

    • Optolong 31mm Round Unmounted 7nm H-Alpha Filter

    • Filter Case

  • Dimensions & Specifications

    • Filter Size: 31 mm

    • Filter Type: Narrowband Imaging

    • Filter Shape: Round

    • Mounted or Unmounted: Unmounted

  • Product Guarantee

    We stand behind all the products we sell, and your satisfaction is our top priority. If you're not satisfied with the quality of your purchase, simply send the item back to us in its original packaging within 30 days of its delivery.

    Manufacturer Warranty

    Two Years

    Return & Exchange Policy

    At our site, returns are easy! You may return new, unused, and resalable items for a refund or exchange. Simply ensure that the item is returned in its original product packaging within 30 days of delivery.

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