Like the O-III filter, the OVL telescope narrow band UHC filter isolates the two lines of ionized oxygen (496 and 501 nm) but also the H-Beta line (486 nm), which is emitted by planetary and most emission nebulae. This filter allows beautiful observation of objects like Orion, Lagoon Nebula, Swan and many other extended nebulae. It is also ideal for smaller telescopes, as it lets more light through than the O-III filter, and it also suppresses light pollution in the sky very well. The UHC filter is the best all-rounder for observing nebulae in the dark night sky. Scope of delivery: Filter 1.25″ storage box! Power supply and batteries are not included!