Lumicon Night-Sky Hydrogen-Alpha Filters

Lumicon's Night Sky Hydrogen-Alpha Filters are long-pass filters with a 50% transition from blocking to passing at about 640nm. At wavelengths longer than 600nm, transmittance is 90% 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.