2nd Quality filters have minor imperfections that do not significantly impact performance.
2nd Quality Lumicon 1.25 Inch UHC FilterLumicon 1.25 Inch UHC 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.
Lumicon filters remain the world’s best and strictest quality control standards are employed throughout the production process. Each Ultra High Contrast Filter is individually inspected and scanned with the percentage of light transmittance of the OIII and H-beta emission lines.