Astromania 2" O-III Filter - produces near-photographic views of the Veil, Ring, Dumbbell and Orion nebula, among many other objects 2" O-III Filter greatly enhances contrast during visual observation of gaseous and planetary nebulae in all sky conditions. Astrophotographic 2" filter allows high-contrast imaging even in areas with strong light pollution. Especially useful for large aperture telescopes through which the light of the Moon can be extremely overwhelming. Allowing just for the Double Ionized Oxygen lines between 496mm to 501nm to pass through at 95%. Completely blocks virtually all other visible wavelengths of light so views of nebulas are optimized. Increases contrast through selective filtration-Anti-reflection coated to prevent glaring and ghosting. Not only useful at light-polluted sites; the contrast is also increased at dark sky sites, can be used with all 2" eyepieces. Filter made from high-grade glass with dichroic interference and antireflection coatings. Each Astromania 2" O-III Filter is individually inspected and proudly inscribed with the percentage of light transmittance of the two O-III emission lines.