
Astronomik CLS-CCD DeepSky & LightPollution Clip-Filter for AstroPhotography
Mounted filter in EOS Clip-cell
The Astronomik CLS CCD is suitable under light-polluted skies for DSLR Cameras, which have been remodeled for astronomical use. The filter enhances the contrast between all deep-sky objects and the background.
If you have an unmodified EOS dslr camera, the slightly cheaper Astronomik CLS filter would be just as useful for you as this item.
Astronomik have re-designed all of their photographic filters. Since the end of 2008 they are shipping their new "Halo-Free" filters.
For full compatibility list please visit the manufacturer's website. Click here!
The CLS-CCD Filter enhances the contrast between astronomical objects and the background. Due to the wider transmission curve compared to UHC filters, a greater amount of light will pass the filter. Stars will be less dimmed. This filter has been optimized to block as much spurious light as possible and simultaneously provide the best performance for 'useful' light. A good filter for DSLR-, CCD- and film b/w-photography as well as observation of deep-sky-objects with telescopes or photo lenses of all aperture f/3 and above.
The filter blocks completely emission lines of artificial light sources like streetlights (e.g. sodium- and mercury-vapor) as well as the airglow. All 'important' emission lines as well as the spectral range of the night-adapted eye are beeing passed. The supplementary IR-blocking layer allows the use for DSLR- and Webcams without an integrated IR-block filter.
CLS: For cameras with an integrated IR-filter or for visual observation.
How to read the above chart?
* The horizontal axis is the Wavelength in Nanometers (nm). 400nm is deep blue, at 520nm the human eye senses green and at 600nm red. At 656nm is the famous "H-Alpha" emission line of hydrogen.
* The transmission in % is plotted on the vertical axis.
* The red line shows the transmission of the filter.
* Visual filters: The grey line filled with grey in the background shows the relative sensitivity of the human eye at night. The maximum is at ~510nm and drops to longer and shorter wavelengths. You can easily see, that you can´t see anything of the H-alpha line at night (even if you can during daylight!) The sensitivity of the eye at 656nm is 0% at night!
* Photographic filters: The grey line in the background shows the sensitivity of a typical CCD sensor.
* The most important emission lines from nebulas are shown in green. The most important lines are from ionized Hydrogen (H-alpha and H-beta) and double ionized oyxgen (OIII) .
* The most important artifical emission lines are shown in orange. The artifical light pollution is dominated by mercury (Hg) and sodium (Na), which are used in nearly all streetlights.
The major emission lines of artifical light pollution:| Hg 435,8nm | Hg 546,1nm | Hg 577,0nm |
| Hg 578,1nm | Na 589,0nm | Na 589,6nm |
| Na 615,4nm | Na 616,1nm |The major emission lines of nebulas: | H-β 486,1nm | OIII 495,9nm | OIII 500,7nm |
| H-α 656,3nm |
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