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Astronomik CLS Light Pollution Filter - 50 mm Square - CLS-50SQ

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SKU: ASF-CLS-50SQ

Astronomik 50 mm Square CLS Light Pollution Filter


  • Suppresses orange glow generated by heavily light polluted urban areas
  • Shows additional stars and more nebulae detail
  • Ideal for telescopes featuring a 1:3 to 1:15 filter to telescope aperture ratio
  • 50 mm x 50 mm square format
  • Offers close to 100% transmission in the 450 nm to 530 nm range of the spectrum including the visual and h-alpha portions
  • Multi-layer coatings on all Astronomik filters provide resistance to the effects of scratching, aging, and humidity
  • Made in Germany, a country well-known for producing high quality optics!


More About the Astronomik 50 mm Square CLS Filter:


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 staying within these aperture ratios, aberrations and coma are eliminated.

Astronomik filters are parfocal with other Astronomik filters. The Astronomik 36 mm CLS Light Pollution Filter has a thickness of only 1 mm. It is highly resistant to scratches and aging effects, as well as high humidity. Diffraction limited, the filter will not reduce the optical performance of your telescope! Astronomik filters include a high-quality, long lasting, plastic storage box.

Transmission Specifications:


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