Lumicon 1.25 Inch Comet FilterLumicon 1. 25 Inch Comet Filter Lumicon 1. 25 Inch Comet Filter is a narrow band pass filter (25nm), which isolates the 501nm OIII line and both C2 lines at 511nm and 514nm. The high contrast of the filter reveals the delicate ionized tail of gaseous comets for optimal viewing. The Comet Filter also helps better distinguish gaseous comets from dusty comets, which normally show little contrast gain. Lumicon filter remains the worlds best and strictest