The original Lumicon Cassegrain Ultra High Contrast Filter is unbeatable for revealing nebulosity. This is achieved by passing three nebula emission lines-the two doubly ionized oxygen lines (496 and 501 nm) and the H-beta line (486 nm)-while blocking light-pollution and Sky Glow. The result is superb views of the Orion, Lagoon, Swan, and other extended nebulae. Recommended for telescopes 8" and larger in aperture. The Lumicon Cassegrain Ultra High Contrast Filter 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 Ultra High Contrast Filter is individually inspected and proudly inscribed with the percentage of light transmittance of the OIII and H-beta emission lines.

• Narrow band pass filter (24 nm) isolates the two doubly ionized oxygen lines (496 and 501 nm) and the hydrogen-beta line (486 nm) emitted by planetary and most emission nebulae
• Provides superb views of the Orion, Lagoon, Swan and other extended nebulae
• The best all-around dark-sky nebular filter available