The 31mm H-alpha 12nm CCD Filter Mounted in Low Profile Non-Threaded Cell by Astronomik 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.
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-percent. 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 guide star.
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.
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. When using the OIII CCD and the 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 a color image. The Astronomik H-alpha filter may NOT be used for solar observation. If you plan to create color images from emission line data, our CLS-CCD filter is a great choice for the Luminance channel.
Now Mounted in Low Profile Non-Threaded Cell: Sometimes unmounted filters can be hard to handle. The smaller diameters, such as this 31mm H-alpha filter, can be especially difficult to pick up and insert or remove from the filter wheel, and that can lead to possible damage as well as unwanted reflections from incorrectly installed filters. Astronomik has solved this problem by mounting their 31mm and 36mm filters in a low profile (3mm) non-threaded cell. O-rings, washers, or spacers are no longer required to hold the filter in place, and because the cell is only 3mm thick, it works well in all appropriately sized filter wheels. Mounted 31mm and 36mm Astronomik filters will also play nice with unmounted versions in the same carousel.
Astronomik H-alpha 12nm CCD Filter - 31mm Round Mounted Features:
- Transmission of over 97-percent with the H-alpha line (656nm)
- Complete blocking from all disturbing wavelengths in the infrared
- Parfocal with other Astronomik filters
- Glass thickness: 1mm
- Cell thickness: 3mm
- 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
OPT Product Number: AK-HA12-31