The Astronomik SII-CCD filter is a narrow-band-filter for CCD photography. The filter lets the light of the doubly ionized sulphur (SII) pass, and blocks nearly the whole remainder of the spectrum, and IR, in which the CCD is sensitive.
The full width at half maximum (FWHM) of 13nm is optimal suitable for common CCD cameras and allows the use of very fast optics. The range of application extends from 1:2.8 to 1:15. Transmission losses and chromatic distortions, which arise with other filters, only occur with Astronomik filters when extremely bright aperture ratios of 1:2 and more come into play. It should be noted that the filter has a transmission of up to 99%, which cannot be attained by stacking more narrow-band filters. A further note, which led to selecting the used FWHM, is the dark current of common CCD imagers. Exposures with a CCD cooled to -15*C are limited by the dark current, even in large cities with a bright background.
Another advantage of the 12nm filters is the good availability of guiding stars for cameras with a built-in-autoguider (SBIG). If you use a very strong filter like our 6nm filter you often won't find a usable guidestar.
The Astronomik SII CCD filter increases the contrast between objects, in this case between those with SII emission lines and the skyglow background. Also, our Astronomik SII-CCD filter completely suppresses the emission lines of artificial lighting (mercury (Hg) and sodium (Na)) and skyglow.
The Astronomik SII CCD increases the contrast between objects, in this case between the SII emission line and the skyglow background. Our Astronomik SII CCD completely suppresses the emission lines of artificial lighting (mercury (Hg) and sodium (Na)) and skyglow. Due to the high optical quality of the Astronomik H-alpha-CCD substrate you will see the same needle-sharp stars as you would from your regular telescope.
- Using the new H-alpha-CCD and the new SII-CCD filters you can obtain three-color images of emission line objects (gas nebulae) from locations with very strong light pollution. To do so, you would take an image in three different wavelengths, select each one as a color-channel in Photoshop and paste them together as one single color image.
- If you plan to create color images from emission line data, our CLS-CCD filter is a great choice for the Luminance channel.
- Visual observation (dark skies): Unsuitable
- Visual observation (urban skies): Unsuitable
- Film photography: It depends, but very long exposure times
- CCD photography: Verry good, huge contrast enhancement at S II-emission nebulas
- DSLR photography (original): Unsuitable
- DSLR photography (astro modified): Verry good, huge contrast enhancement at S II-emission nebulas
- DSLR photography (MC modified): Verry good, huge contrast enhancement at S II-emission nebulas
- Webcam / Video (Planets): Unsuitable
- Webcam / Video (Deep Sky): Unsuitable