Astronomik SII CCD Filter, 12 nm, Clip-Filter EOS XL

This H-alpha Filter is suitable for imaging of Hydrogen nebulas from observation sites with light pollution and from dark sites as well. The contrast between an object glowing at 656nm and the background is increased enormous!

This SII Filter is suitable for imaging of SII-regions from observation sites with light pollution and from dark sites as well. The contrast between an object glowing at 672nm and the background is increased enormous!

Due to the combination of the narrow bandwidth of 12nm and the high transmission of typically 96% the filter gives you an contrast boost, as all unwanted light from other wavelengths than 672nm is blocked form UV up to the IR. This results in an very dark background compared with any filters with a higher bandwidth
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 fluy coming from light pollution. In this case a further reduction of FWHM 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!

Due to the new MFR coating technique you may use one single filter on all instruments up to f/3 without a significant reduction in performance.