Astronomik CLS CCD Deep Sky & Light Pollution Filter 31mm Mounted
Astronomik 31mm CLS CCD DeepSky & LightPollution Filter for AstroPhotography
Filter mounted in a 31mm 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.
Astronomik have re-designed all of their photographic filters. Since the end of 2008 they are shipping their new "Halo-Free" filters.
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.
- Easier resolution of Double Stars.
- With the EOS-Clip model, photography with DSLR cameras is feasible even unter extreme light-polluting conditions without shifting the white balance.
- The 1,25" and 2" socket models can be used for observations from light-polluted areas.
- If you plan to create color images from emission line data, our CLS-CCD filter is a great choice for the Luminance channel
CLS: For cameras with an integrated IR-filter or for visual observation.
- Visual observation (dark skies): Good, to reduce light pollution by mercury-vapour lamps (streetlight)
- Visual observation (urban skies): Reasonable, an UHC-E or UHC filter is more suitable
- Film photography: Very good, colour balance is near perfect
- CCD photography: Very good, optimized rejection of light pollution
- DSLR photography (astro modified): Very good, colour balance is near perfect
- DSLR photography (MC modified): Very good, colour balance is near perfect
- DSLR photography (original): Very good, colour balance shifted but contrast enhanced
- Webcam / Video (Planets): Unsuitable
- Webcam / Video (Deep Sky): Very good, if light pollution is a big problem
- 97% transmission at 656nm (H-alpha)
- 95% transmission at 486nm (H-beta)
- 95% transmission at 496nm (OIII)
- 95% transmission at 501nm (OIII)
- pass from 450 to 520nm and from 640 to 690nm
- Parfocal with other Astronomik filters
- Glass thickness: 1mm
- Diffraction limited, the filter will not reduce the optical performance of your telescope!
- Completely resistant against high humidity, scratches and aging effects
- Astronomik filters are delivered in a high-quality, long lasting, filter box
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 |
|Weight in Kg||0.3|