Chroma H-alpha filter, 5nm FWHM


  • H-alpha filters are essential for imaging nebulae and other objects which are rich in ionized hydrogen.
  • At 656.3nm, a narrow-band emission filter is required to separate H-alpha from the SII doublet (671.6nm and 673.1nm).
  • Parfocal for systems f/4.0 or slower
  • Transmitted wavefront better than 0.25 waves/inch
  • Parallelism: less than 30 arcsec
  • Made in the U.S.A.
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H-α (hydrogen-alpha) at 656 nm (nanometers) is deep red in color and the most popular narrowband filter. Hydrogen is ubiquitous in the cosmos and is present in emission nebula (North American, Pelican), planetary nebula (Dumbbell, Ring), Wolf-Rayet objects (Crescent, Thor’s Helmet) and supernova remnants (Veil). Many imagers like to present just a black-and-white H-α image of an object. It is has a beauty all by itself, like an Ansel Adams photo. However, most imagers blend their H-a data into their red RGB data to enhance structural detail while maintaining a “natural” look. Therefore, the H-α filter should be your first narrowband addition to your LRGB filters. The basic imaging set of 5 filters becomes LRGBH-α.

Weight .3125 lbs
Dimensions 3 × 3 × 3 in
Filter Size

Chroma 1.25" Mounted 5nm H-α – CH_HA5_125R – $460, Chroma 2" round mounted 5nm H-α – CH_HA5_2R – $740, Chroma 5nm H-α unmounted 31mm – CH_HA5_31R – $465, Chroma 36mm Unmounted 5nm H-α – CH_HA5_36R – $620, Chroma 50mm diameter round, unmounted 5nm H-α – CH_HA5_50R – $725, Chroma 50mm square Unmounted 5nm H-α – CH_HA5_50S – $725, Chroma 65mm square Unmounted 5nm H-α – CH_HA5_65S – $1195

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