Astronomik Filters CLS 50mm filter, mounted (52908)

The Astronomik CLS filter is an affordable solution designed for visual observation, black-and-white photography, and CCD imaging of nebulae, galaxies, and star clusters. It is compatible with astronomical instruments of any size. Since late 2008, the filters have been redesigned to eliminate halos and unwanted reflections.

Key Features

• Light Pollution Reduction: The filter blocks spectral lines from mercury and sodium-vapor lamps while allowing most visible light and H-alpha emissions to pass through. This enhances the visibility of important emission lines and the spectral range perceptible to dark-adapted eyes.
• Compatibility: Optimized for aperture ratios between 1:3 and 1:15. Transmission losses and chromatic distortions only occur with extremely bright aperture ratios (e.g., 1:2 or more). Suitable for telescopes of all aperture sizes.
• Durability: Resistant to high humidity, scratches, and aging effects. The filter is diffraction-limited, ensuring no reduction in optical performance.

Specifications

• Transmission Rates:
  • 92% at 486nm (H-beta)
  • 92% at 496nm (OIII)
  • 92% at 501nm (OIII)
  • 97% at 656nm (H-alpha)
• Wavelength Range: Passes light from 450-540nm and beyond 650nm.
• Build: Aluminium frame with a glass thickness of 1mm.
• Design Improvements: "Halo-Free" design introduced in 2008.

Applications

• Visual Observation:
  • Effective in dark skies for reducing light pollution from mercury-vapor lamps.
  • In urban skies, an alternative like UHC-E or UHC filters may be more suitable.
• Photography:
  • Excellent for film photography with near-perfect color balance.
  • Good for DSLR photography (original cameras) with enhanced contrast but shifted color balance.
  • Very effective for astro-modified DSLRs with near-perfect color balance.

The Astronomik CLS filter is available in various formats, including sizes like Ø50mm, T-thread cells, and clip-in models for DSLR cameras.