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Astronomik H-alpha 12nm Filter
The Astronomik H-alpha filter is a narrow band filter for CCD photography. The filter lets the H-alpha light of emission nebulae pass and blocks nearly the whole remainder of the spectrum where the CCD is sensitive.
We have re-desgined all of our photographic filters. Since the end of 2008 we are shipping our new "Halo-Free" filters. read more...
The full width at half-maximum (FWHM) of 12nm is optimized for the use with common CCD cameras and allows the use of very fast optics. It should be noted that the filter has a transmission of up to 99%.
Another advantage of the 12nm filters is the 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 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.
Main use
The Astronomik H-alpha-CCD (12nm version) increases the contrast between objects, in this case between the H-alpha emission line and the skyglow background. Our Astronomik H-alpha-CCD (12nm version) completely suppresses the emission lines of artificial lighting (mercury (Hg) and sodium (Na)) and skyglow.
