The ULTIMATE nebula filter. The original Lumicon 1.25in 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 501nm) and the H-beta line (486nm)-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.