Astronomik CLS Light Pollution Filter - 1.25" Mounted

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Astronomik CLS Light Pollution Filter - 1.25" Mounted

The CLS Light Pollution Filter - size 1.25-Inch,  Round by Astronomik:

The Astronomik CLS is an excellent filter for black and white and color imaging of nebulae, galaxies and star clusters with astronomical instruments of any size. By blocking the spectral lines of mercury and sodium-vapor lamps, and letting the largest part of the visible light and H-alpha emissions pass, the CLS filter will effectively block out most surrounding light pollution, eliminating that annoying orange glare.

The filters are optimized for use with filter to aperture ratios of 1:3 to 1:15. By remaining within these aperture ratios, aberration and comma are eliminated.


Astronomik CLS Light Pollution Filter - Transmission Information:

  • 92-percent transmission at 486 nm (H-beta)
  • 92-percent transmission at 496 nm (OIII)
  • 92-percent transmission at 501 nm (OIII)
  • 97-percent transmission at 656 nm (H-alpha)
  • Pass from 450 to 540 nm and beyond 650 nm


  • Parfocal with other Astronomik filters
  • Glass thickness: 1 mm
  • Highly 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-CLS-1 



Filter TypeLight Pollution/City Light Suppression
Free ShippingYes
Peak Transmission97% at H alpha
Warranty10 Year Warranty
Customer Reviews
5.0 Based on 2 Reviews
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Filter Reviews:
Marcelo C.
United States United States
Great filter

This filter has excellent transmission on the wavelengths that are needed for Astro Photography and good light pollution suppression. I’ve been able to imaging galaxies with relatively low exposure time in bortle 8 sky

Gilbert R.
United States
visual filters

wanting to see DSO's better. The people at OPT were helpful in explaining the difference and use of visual and imaging filters. service was prompt.