The Lumicon 1.25", 2", and 2" Cassegrain, Comet Filters, are narrow band-pass filters (25nm), that isolate 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, allowing you to see their full extent. The Comet Filter also helps you to better distinguish gaseous comets from dusty comets, which normally show little contrast gain.
The Cassegrain filter cell threads onto your telescope's SCT rear-cell, and presents male SCT threads for accessory attachment. The Cassegrain filter cell allows you to change eyepieces without threading/unthreading the filter, and is also easier to change-out than the standard 2" filter cell with gloves on, for cold-weather observing.
To ensure that your Lumicon filter remains the World's Best, the strictest quality control standards are employed throughout the production process. Each Lumicon Comet Filter is individually inspected and proudly inscribed with the percentage of light transmittance of the primary emission lines at 501, 511 & 514nm.