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Astronomik SII 6 nm CCD Filter - SC Rear Cell - SII6-SCT

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SKU: ASF-SII6-SCT

Astronomik SII 6 nm CCD Filter - SCT Rear Cell


  • This Astronomik SII 6 nm CCD Filter in SC rear cell format was created for the express purpose of CCD astrophotography with Schmidt-Cassegrain telescopes
  • Designed with the highest technical standards in mind to enable peak optical performance for deep sky imaging applications with your CCD camera
  • Ionized sulfur (SII) light is allowed to pass while the complete rest of the visual spectrum as well as IR is cut off
  • FWHM bandwidth is close to 12 nm
  • Best suited for imaging planetary neblae as well as the remains of supernovae
  • Made in Germany, a country recognized for producing optics of superior quality!


More About Astronomik SII 6 nm CCD Filters

For CCD astrophotography operations, the SII 6 nm CCD Filter from Astronomik is the ideal narrowband filter. It has a smaller full width at half maximum (FWHM) of 6 nm to enable higher contrast gain than you would get from the 12 nm filter when also factoring in a typical 96% transmission given that all unwanted light from alternate wavelengths from UV up to IR is blocked. This results in an especially dark background. While you may experience transmission reductions and chromatic distortions with other filters, these only occur with Astronomik filters when exceptionally bright 1:2 and above aperture ratios are involved.

With its smaller 6 nm FWHM, this Astronomik SII CCD Filter is ideal for exhibiting the maximum amount of contrast between objects that emit SII light, such as emission nebulae and the skyglow background. 6 nm filters offer similar performance when compared with 12 nm filters, but also provide a higher contrast gain. On the contrary, using a 6 nm FWHM filter can cause background stars to appear dimmer, or to not be viewable at all. Thus, to achieve maximum contrast without sacrificing the background quality of your final image, it is best to employ both the 6 nm and 12 nm SII filters together.

This Astronomik SII 6 nm CCD Filter enables complete blockage of all unwanted wavelengths in the visible and IR bands of the spectrum. As with all filters from Astronomik, this filter is parfocal with all other Astronomik filters. It is also diffraction limited so it won't compromise the optical performance of your telescope. Coatings keep this SII CCD filter from inducing scratches and other damaging effects from aging and high humidity. All Astronomik filters are delivered in a long-lasting plastic filter case of supreme quality.

Transmission Specifications


  • Over 97% ionized sulfur (SII) line transmission
  • Obstructs nearly the entire remainder of the visible spectrum
  • Blocks unwanted wavelengths in the Infrared