Astronomik Sulphur-II (SII) Narrowband 12nm CCD Filter (1.25")

Astronomik Sulphur-II (SII) Narrowband 12nm CCD Filter (1.25")

Due to high demand and global product shortages due to the pandemic, please call for availability.

If you have to observe from light polluted sites (like most of us), imaging with narrowband emission line filters is the best way to take great images, as all kind of light pollution can be blocked very effectively! The image(s) taken with an SII filter, when combined with images from H-Alpha and OIII filters allows you to create a final 3 channel colour Hubble palette image, just like the ones taken by the Hubble Space telescope.

The contrast between an object glowing at 672nm and the background is increased enormously.

Due to the combination of the narrow bandwidth of 12nm and the high transmission of typically 96%, the filter gives you an enormous contrast boost, as all unwanted light from wavelengths other than 672nm is blocked, from UV up to IR. This results in an extremely dark background. The FWHM of 12nm is optimized for typical DSLR cameras with CMOS sensors and CCD cameras with a normal/high dark current. With these cameras the background signal in images taken from heavily light polluted sites is dominated by the dark current of the sensor, not by light coming from light pollution. So a further reduction of FWHM to 6nm does not improve the image, as the background will not get darker. Compared to the 6nm filters you have more stars in the field of view which gives you more guiding stars when working with an integrated/dual guiding chip.

This filter is not for solar observation.

Price does not include shipping from Germany, which is separate from the possible free shipping from us to you. You will be notified of these shipping charges prior to payment being taken.


  • Guaranteed transmission of more than 90% at the SII line (672nm)
  • Typical Transmission of 96% at the SII Line (672 nm)
  • Full-Width-Half Maximum (FWHM): 12nm
  • Perfect blocking of unwanted light from UV up to the IR
  • parfocal with all Astronomik filters
  • MFR coating technique: usable with all optics up to f/3
  • Thickness: 1mm
  • Not sensitive to moisture, scratch resistant, non-aging
  • opticaly polished substrate, striae-free and free of residual stresses
  • High quality storage box
  • Made in Germany