The Ultra High Contrast (UHC) Filter is the best all-around dark-sky nebula filter. This filter permits superb views of objects like the Orion, Lagoon, Swan and other extended nebulae. It performs well in smaller aperture instruments owing to its greater light transmission than the O-III, yet still suppresses light pollution well. Supplied with storage case.
High Contast Filter :
The narrowband UHC filter, like the O-III filter, isolates the two doubly ionized oxygen lines (496 and 501nm) in addition to the hydrogen-beta line (486nm) emitted by planetary and most emission nebulae.