Astronomik CLS Light Pollution Filter - 1.25" Mounted

Astronomik CLS Light Pollution Filter - 1.25" Mounted
Item # AK-CLS-1
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  • The Astronomik CLS Filter will eliminate the orange glow caused by urban lighting.
  • This CLS filter is mounted in a 1.25" cell.
  • The Astronomik CLS Filterprovides nearly 100% transmission between 450nm and 530nm which includes the visual and h-alpha portion of the spectrum.
  • Optimized for telescopes with a filter to telescope aperture ratio of 1:3 to 1:15.
  • The multi-layered coatings on all Astronomik filters protect amazingly well against scratching, aging, and humidity.
  • The Astronomik CLS Filter shows more stars and detail in nebulae.


Astronomik CLS Light Pollution Filter - 1.25" Round

The Astronomik CLS is an excellent filter for black & 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% transmission at 486nm (H-beta)
  • 92% transmission at 496nm (OIII)
  • 92% transmission at 501nm (OIII)
  • 97% transmission at 656nm (H alpha)
  • Pass from 450 to 540nm and beyond 650nm


  • Parfocal with other Astronomik filters
  • Glass thickness: 1mm
  • 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
Additional Information

Additional Information

Manufacturer Astronomik
Type of Filter Light Pollution Reduction
Filter Usage Imaging, Visual
Single or Set? Single Filter
Filter Size 1.25"
Filter Shape Round
Filter Mounted? Mounted
Warranty 10 Year Warranty
Peak Transmission 97% at H-alpha
Included Items

Included Items

  • Astronomik 1.25" CLS Light Pollution Filter
  • Plastic Storage Case
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