A. About Optolong's Moon and Skyglow FIlter

Optolong's Moon & Skyglow filter is designed to darken the background sky by blocking light transmission from skyglow (589nm) and many street light emissions from artificial light. Its high efficiency preserves image brightness, reveals more details and increases contrast of moon, galaxies, nebulae and globular star clusters.

B. Main Uses and Performance

• This is a versatile filter for visual observation and astrophotography of planetary nebulae.
• Enhance contrast of moon, galaxies, nebulae and globular star clusters.

C. Spectral Curve Transmission Characteristics

• This version does not block out infrared wavelengths (700-1100nm) so a separate IR cut-off filter is recommended for imaging applications.

D. Technical Specifications

• Both surfaces are fine optically polished, accurate to 1/4 wavelength or better, and parallel to within 30 seconds or arc.
• 2mm thick Schott B270 optical glass substrate material.
• Very high surface quality of 60/40 or better (US Military Spec MIL-O-13830).

E. Optical Coating Specifications

• Multi layer anti-reflection coated.
• Non-cementing optical substrate coating.
• Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength) so that there is no deviation due to temperature changes during use.
• Precise and homogeneous coatings ensure high values of desired passband and blocking of unwanted offband.
• Every single filter is tested and passed by Optolong before shipping to dealers.

F. Other

• 1.25" astronomy filter with standard M28.5x0.6 male filter thread (no female thread, so it cannot be stacked with other filters).
• Ultra-thin filter cell to minimize vignetting; clear optical aperture of 26mm.
• Precision CNC-machined metal filter cell with sand blasted black anodized finish, anti-reflection treatment, and laser engraving.
• High quality protective plastic storage case.

WARNING: Optolong filters are not designed for direct solar observation. NEVER use these filters for observing the Sun, or permanent eye and equipment damage will result.