Optolong Moon & Skyglow filter 2"

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.   1.  Moon & Skyglow Introduction Optolong 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. Main Use Ideally it is quite versatile filter for visual observation and astrophotography on planetary nebula. WARNING: The filters of Optolong are not designed for sun observation. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTER. You would be BLIND if you fail to observe the warning.   2. Moon & Skyglow Spectrum and Characteristic Sbustrate: B270 Thickness: 1.85mm Tave:  T>90% Blcoking depth: light pollution  line blocking >99% Surface quality: 60/40 Transmitted Wavefront RMS: λ/4  Parallelism: 30s     How to read the chart? ▲The horizontal axis is the Wavelength in Nanometers(nm). ▲The vertical axis is transmission in %.   3. Coating Technology ·Multi-layers anti-reflection coating ·Non-cementing optical substrate coating ·Optolong L-Pro filter adopts precision coating based on Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL(central wavelength) no deviation affected by temperature change. ·Planetary rotation system offers precision and homogeneity of coatings ensuring high value on transmission of pass-band and Optical density of off-band.