Astronomik H-Alpha 12nm CCD Filter - 31mm Round Unmounted
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.
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.
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. f you plan to create color images from emission line data, our CLS-CCD filter is a great choice for the Luminance channel.
Astronomik H-Alpha 12nm CCD Filter - 31mm Round Unmounted Features...
- Transmission of over 97% with the H-alpha line (656nm)
- Complete blocking from all disturbing wavelengths in the infrared
- 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
Relative transmission curve of an Astronomik CCD Ha filter (filter number 1). From left to right the dashed lines indicates the position of Hb (bleue), [OIII] doublet (green), Ha at 6563 A (red) and [SII] line at 6730 A (cyan).
Detail of an Astronomik CCD Ha filter transmission near Halpha line (red dashed line). Filter #1
Relative transmission curve of an Astronomik CCD Ha filter (filter number 2). From left to right the dashed lines indicates the position of Hb (bleue), [OIII] doublet (green), Ha at 6563 A (red) and [SII] doublet at 6730 A (cyan).
The central wavelength of the filter #2 is significantly shifted toward the bleue. Efficiency at the Halpha level is reduced by a factor 0.9 comparatively to an hypothetical correct filter. The proof...
Up image, part of the sun spectrum taken with the LISA spectrograph (intermediate resolution mode - 600 grooves/mm grating). Middle image, same observation condition, only the Astronomik Ha filter #2 is added in the optical beam. The red shift of the transmission curve relative to the Halpha line position is very evident. Down image, an Edmund Optics Halpha is now used (ref. 43-086). The central wavelength position is now correctly adjusted (but in the same time the peak transmission of the Edmund filter is near 50% only, and near 90% for the Astronomik filter).
The Astronomik CCD Halpha filter #2 for two incident angles. The curves show progression in pass-band when the angles of incidence of the f/8 beam are varied from 0° to 5° (simulate approximately the marginal rays of a f/5.6 telescope). The dashed line indicate the position of Ha.
Relative transmission curve of an Astronomik CCD SII filter. The red dashed line indicate the position of Ha line (at 6563 A). The magenta lines indicate the position of [SII] doublet (at 6719 and 6730 A).
|Name||Astronomik - H-Alpha 12nm CCD Filter - 31mm Round Unmounted|
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