Chroma SII filter, 5nm FWHM


  • SII filters isolate the spectral emission of singly ionized sulfur atoms, also common in nebulae. Emission is at two lines occurring as a doublet, at 671.6 and 673.1 nm. This filter also separates sulfur emission from H-alpha emission (656.3nm).
  • 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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If you want the look of Hubble Space Telescope (HST) images, such as the famous “Pillars of Creation” (the Eagle Nebula, Messier 16), then the next filter to consider adding to your collection after H-a and OIII is the SII (es-two) or sulfur filter. The SII filter, like H-a, is a deep red filter near 672 nm. H-a, OIII and SII filters provide that Hubble look for many emission nebula. Again, tri-color narrowband imaging with these three filters can be done with the moon up, so your equipment is not sitting dormant for several weeks.

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

Chroma 1.25" Mounted 5nm SII – CH_SII_125R – $460, Chroma 2" round mounted 5nm SII – CH_SII5_2R – $740, Chroma 5nm SII unmounted 31mm – CH_SII5_31R – $465, Chroma 36mm Unmounted 5nm SII – CH_SII5_36R – $620, Chroma 50mm diameter round, unmounted 5nm SII – CH_SII5_50R – $725, Chroma 50mm square Unmounted 5nm SII – CH_SII5_50S – $725, Chroma 65mm square Unmounted 5nm SII – CH_SII5_65S – $1195

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