Celestron - Oxygen III Narrowband Filter - 2 in

The 2" OIII narrowband filter isolates just the two doubly-ionized oxygen lines (496 and 501nm 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.