Astronomik CLS Clip-Filter Pentax K

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Astronomik CLS Clip-Filter Pentax K

The Astronomik CLS filter is best used for photographs of nebulae, galaxies, and star clusters. Astronomical instruments of any size can be used with this filter.

This filter blocks the spectral lines of light for mercury and sodium-vapor lamps while letting the largest portions of visible light and H-alpha emissions pass. All important emission lines can pass through the filter, as well as the spectral region that very well-adapted eyes are able to see.

Astronomik CLS Clip Filter

The Astronomik CLS filters offer a transmission rate of 97% for H-beta (486nm), OIII (496nm), OIII (501nm), and H-alpha (656 nm) with a glass thickness of 1mm. For optimal performance, these filters are best used with telescopes with focal ratios between f/3.5 and f/10. These are also both scratch-resistant and not sensitive to humidity or aging with their excellent craft materials. These filters will not reduce the optical performance of your telescope and are parfocal with other Astronomik filters

Another major advantage of the Astronomik CLS filter is the high optical quality of the filter glass. When using Astronomik CLS filters you will quickly notice the same needle-sharp stars which you are familiar with from your astronomical instrument without any filter!


  • Visual Observation (Dark Skies): Good to reduce light pollution by mercury-vapor lamps (common streetlights)
  • Visual Observation (Urban Skies): Good but a UHC-E or UHC filter is more suitable
  • Film Photography: Very good with near perfect color balance
  • CCD Photography: Good when used with an additional IR-block-filter
  • DSLR Photography (Original): Good yet slightly shifted color balance shifted and with enhanced contrast
  • DSLR Photography (Astro Modified): Very good with near perfect color balance
  • DSLR Photography (MC Modified): Good when used with an additional IR-block-filter
  • Webcam / Video (Planets): Unsuitable
  • Webcam / Video (Deep Sky): Very good if light pollution is a big problem


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