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Astronomik SII 12 nm CCD Filter - 31 mm - SII-31

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SKU: ASF-SII-31

Astronomik SII 12 nm CCD Filter - 31 mm


  • This Astronomik SII CCD Filter is designed for astrophotography and comes in a thin, round 31 mm threaded cell
  • Created with the highest technical standards in mind to offer the optical efficiency needed to perform deep sky imaging operations with your CCD camera
  • Allows ionized sulfur (SII) light to pass while blocking almost the entire remainder of the visual spectrum along with IR
  • The Astronomik SII CCD Filter has an approximately 12 nm FWHM
  • An excellent filter for imaging planetary nebulae and remnants of supernovae
  • German-designed for high optical quality!


More About the Astronomik 31 mm SII 12 nm CCD Filter


For CCD astrophotography applications, you would be hard pressed to find a more ideal narrowband filter than the Astronomik SII 12 nm CCD Filter. Its 12 nm FWHM (full width at half maximum) is optimal for standard CCD cameras, enabling the use of extremely fast optics. The f/number application range spans from 1:2.8 to 1:15. Transmission reductions and chromatic aberrations, sometimes an issue with other filters, only arise with Astronomik filters when severely bright 1:2 and more aperture ratios are involved. A further advantage of 12 nm filters is the improved availability of guide stars for cameras featuring a built-in autoguider. Up to 99% transmission.

Astronomik's CCD filters enhance the contrast between objects. The SII filter enhances contrast between SII emission line objects and the background sky while offering total suppression of mercury (Hg) and sodium (Na) and other artificial light emissions, as well as skyglow, making it an excellent filter to use in light polluted conditions. Because of the high quality of the Astronomik SII 12 nm CCD substrate, you'll see the same razor sharp stars as you would from your regular telescope.

This 31 mm Round SII 12 nm CCD Filter from Astronomik provides complete blockage of all superfluous wavelengths in the visible and IR spectral bands. It has a very thin substrate, and is parfocal with all other Astronomik filters. Diffraction limited, this filter will not reduce the optical performance of your telescope. Coatings offer complete protection from scratching as well as the impacts of aging and high humidity. All Astronomik filters are delivered in a durable, high quality plastic filter box.

Transmission Specifications


  • Over 97% transmission for the ionized sulfur (SII) line
  • Blocks close to the entire remainder of the visual spectrum
  • Blocks undesired infrared wavelengths