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Astronomik CLS Lens Filter

Product information "Astronomik CLS Lens Filter"

The Astronomik CLS filter is designed for visual observation and photography of nebulae, galaxies, and star clusters using telescopes and lenses. It completely blocks the emission lines from high- and low-pressure sodium (Na)- and mercury (Hg)-vapor lamps, the majority of emissions from LED lamps as well as all lines of natural airglow while allowing the majority of visible light and nebulae emissions to pass through. This enhances the contrast between deep-sky objects and the night sky, making it ideal for photography and observation in light-polluted areas.

Due to its wide passband, the Astronomik CLS filter passes a substantial amount of light, minimally dimming stars. The filter is designed to block as much unwanted light as possible while still transmitting the maximum amount of light from astronomical objects.

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20s exposures with JPEG data directly from the camera without further processing. Second image taken with the Astronomik CLS filter. (Canon EOS 6D astro-modified, ISO 6400, Canon EF24-105mm f/4L IS II USM @ 24mm / f/4)

Other uses

The 1.25" and 2" socket models can be used for observations from light-polluted areas.

Alternatives

If there is no built-in IR cut filter in your camera, a Astronomik CLS CCD filter is required.

Suitability of the Astronomik CLS filters

  • CMOS and CCD photography: Good, requires an additional Astronomik IR-Block filter
  • DSLR photography (original): Good, color balance is shifted but contrast is enhanced
  • DSLR photography (astro-modified): Very good, color balance is close to perfect
  • DSLR photography (MC-modified): Good, requires an additional Astronomik IR-Block filter

Gallery of images taken with our Astronomik CLS CCD filter (using the Astronomik CLS filter with a respective camera will result in identical images)

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Technical Data

  • 92% transmission at 486nm (H-beta)
  • 92% transmission at 496nm (OIII)
  • 92% transmission at 501nm (OIII)
  • 97% transmission at 656nm (H-alpha)
  • Transmission range: 450 to 540nm and above 650nm
  • Glass thickness: 1mm (except Astronomik OWB Type 3 and XT filters)
  • Finely polished optical glass, free of any striae, residual stresses, and bubbles
  • Extremely scratch-resistant and durable coating
  • Completely resistant against high humidity and aging effects
  • Astronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)
  • Parfocal with other Astronomik filters
  • Diffraction-limited
  • Optimized spectral windows
  • Delivered in a high-quality, long-lasting filter box

Due to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated. 

All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures. The Astronomik MFR coating is designed for optimal performance across a wide range of focal ratios of the optics used.

Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios.