A filter with incredible light pollution cut off characteristics The new H-Alpha passfilter enables high-contrast deep sky images of H-II regions The H-Alpha filter shares the same outstanding features as all the other Astromania imaging filters Unmatched optical quality and high efficiency hardened multicoatings result in the sharpest and highest contrast images possible The filter is used as an extreme anti light-pollution filter and for contrast-enhancement of emission nebulae and other astronomical objects bright in the infrared The Night Sky Hydrogen-Alpha Filters are long-pass filters with a 50% transition from blocking to passing at about 640nm. At wavelengths longer than 650nm, transmittance is 80% or above. The filter is used as an extreme anti light-pollution filter, and for contrast-enhancement of emission nebulae and other astronomical objects bright in the infrared. The 1.25" Night Sky Hydrogen-Alpha Filter, threads into the nose-piece of industry-standard 1.25" Digital Imagers. The Astromania H-Alpha cut-off filter enhances the contrast between object and sky, allowing you to take good quality images even under urban skies.