Astronomik CLS Filter

The Astronomik CLS is a budget filter for visual observation, Black & White photography and CCD photographs of nebulae, galaxies and star clusters with astronomical instruments of any size.

The Astronomik CLS blocks the light of the spectral lines of mercury and sodium-vapor lamps and lets the largest part of the visible light and H-alpha emissions pass. All the important emission lines, as well as the spectral region that the very well dark adapted eye can see, can pass through the filter.

Main use

The filters are optimized for use with aperture ratios from 1:3 to 1:15. Transmission losses and chromatic distortions, which are problems with other filters, only appear with Astronomik filters when extremely bright aperture ratios of 1:2 and more are used. The CLS filter is suitable for use with telescopes of all aperture sizes.

Technical Data

• 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
• Completely 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
• Since 2008 we do ship filters with a completely new design. Any kind of halo or strange reflection is a matter of past

Suitability

• Visual observation (dark skies): Good, to reduce light pollution by mercury-vapour lamps (streetlight)
• Visual observation (urban skies): Good, an UHC-E or UHC filter is more suitable
• Film photography: Very good, colour balance is near perfect
• CCD photography: Good, when used with an additional IR-block-filter
• DSLR photography (original): Good, colour balance shifted but contrast enhanced
• DSLR photography (astro modified): Very good, colour balance is near perfect
• 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