The Astronomik 6nm H-alpha filter is an extremely narrow emission-line 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.
The full width at half-maximum (FWHM) of 6nm is optimized for a maximum contrast between the (H-alpha emitting) object and the background. The contrast gain is much higher than with our 12nm emission line filters but you won’t see as much stars in the resulting images.
The design of the transmission curve makes it possible to use the filters with instruments from 1:3.75 to 1:15. Selected filters for faster system are available upon special request.
All transmission curves of the 6nm filter are measured individually. Because of this procedure you can get the optimum filter for your telescope: If you place a direct order please specify the focal ratio of your instrument and we will select the best filter for your setup. So you may get the best filter without paying for an A+ filter.
Main use
The Astronomik H-alpha-CCD (6nm version) increases the contrast between objects, in this case between the H-alpha emission line and the skyglow background in the same way as the 12nm version. The gain in contrast is much higher due to the smaller FWHM. The 6nm H-Alpha filter is the right choice for extremely dim objects, even in the milkyway, and for observations from heavily light-polluted places. The Astronomik 6nm H-alpha-CCD completely suppresses the emission lines of artificial lighting (mercury (Hg) and sodium (Na)) and skyglow. Transmission losses and chromatic distortions, which arise with other filters, only occur with Astronomik filters when extremely bright aperture ratios come into play. Selected filters for faster systems are available upon special request.
Other uses
- Using the Astronomik 6nm H-Alpha together with the 12nm H-Alpha gives you the ability to have a maximum contrast in the HII objects and to keep the stars in the final image.
- The Astronomik 6nm H-Alpha filter may NOT be used for solar observation.
Suitability
- Visual observation (dark skies): Unsuitable
- Visual observation (urban skies): Unsuitable
- Film photography: Unsuitable
- CCD photography: Very good, huge contrast enhancement at H II-emission nebulas
- DSLR photography (original): Good, reduced sensitivity in the H-alpha band
- DSLR photography (astro modified): Very good, huge contrast enhancement at H II-emission nebulas
- DSLR photography (MC modified): Very good, huge contrast enhancement at H II-emission nebulas
- Webcam / Video (Planets): Unsuitable
- Webcam / Video (Deep Sky): Unsuitable
Technical Data
- typ. transmission von über 90% at H-Alpha (656nm)
- Parfocal with other Astronomik filters
- Glass thickness: 1mm
- Completely resistant against high humidity, scratches and aging effects
- Diffraction limited, the filter will not reduce the optical performance of your telescope!
- Astronomik filters are delivered in a high-quality, long lasting, filter box
- Since 2008 we do ship filters with a completely new design. Any kind of halo or strange reflection is a matter of past
