The 2" OIII narrowband filter isolates just the two doubly-ionized oxygen lines (496 and 501 nm lines) emitted by planetary and emission nebulae, while blocking the rest of the overall spectrum of light. The result is extreme contrast between the black sky background and the faint photons of OIII light needed for detailed views of the Veil, Ring, Dumbbell, Crescent and Orion nebulae, among other objects. Each filter has an ultra hard, vacuum-deposited coating carefully designed to block all of the visual spectrum ranging from 400 to 700 nm This eliminates the un-natural colored halos surrounding bright stars common with O III filters of less sophisticated coating technology. The Celestron 93624 Narrowband Oxygen III 2-inch filter is a remarkable advance for the serious visual observer of emission nebulae. One of the biggest advantages of narrowband filters is that by passing only the light emitted by nebulae, light from artificial sources like street lights is blocked. This allows you to take detailed exposures of nebulas from a suburban location that can rival shots from much darker sites. The Celestron 93624 is made of high quality, solid plane parallel glass.

Country of Origin:China. Eliminates un-natural colored halos surrounding bright stars. Filter has ultra-hard, vacuum-deposited coating. The 2" OIII narrowband filter isolates the two doubly-ionized oxygen lines (496 and 501 nm lines).

Water Resistance Level: Not Water Resistant. Photo Filter Effect Type: Neutral Density. Coating Description: Multi Coating. Photo Filter Thread Size: 50.8 Millimeters. Material: Glass. Brand: Celestron. Country of Origin: China. Manufacturer: Celestron. Date First Available: June 17, 2003. Is Discontinued By Manufacturer: No. Best Sellers Rank: #136 in Telescope Filters. Customer Reviews: 4.6 out of 5 stars 48 ratings 4.6 out of 5 stars. Item model number: 93624. : B0007UQNWM. Item Weight: 0.8 ounces. Product Dimensions: 1.87 x 1.87 x 0.25 inches.