Optolong OIII CCD 3nm 2" Mounted Filter

Optolong uses a multi-layer, anti-reflection coating on the filter. It uses a non-cementing optical substrate coating, applied through precision Ion-based deposition, providing durability and resistance to scratching. It also provides stability on the central wavelength so there is no deviation depending on temperature change. Their planetary rotation system gives precision and homogenous coatings to ensure high-value pass-band transmission and off-band optical density.

OIII (Oxygen IIII) CCD filters like this 36 mm Optolong OIII extra narrowband filter, allow a 3nm bandwidth of light, centered on a 500nm wavelength, through. This corresponds with the OIII emission line. OIII filters emit 495.9nm and 500.7nm and are blue-green colored filters.

This OIII CCD filter reduces certain types of light transmission like artificial light from mercury vapor and both high/low-pressure sodium vapor lights. They also block natural light transmissions caused by neutral oxygen emission in our atmosphere, often called sky glow.