The OVL O-III narrow band filter was specially developed for observing gas and planetary nebulae with your telescope. It only lets through a very narrow range of wavelengths of visible light, increasing the contrast, giving you ideal conditions for observing super nova remnants and planetary nebulae. The O-III narrowband filter isolates only the two lines of ionized oxygen (496 and 501 nm) emitted by diffuse planetary nebulae and extremely faint nebulae. O-III filters work ideally with larger telescopes from 200 mm aperture. With larger telescopes, the observer has better opportunities to identify nebulae in the sky. It can produce near-photographic views of objects like the Ring Nebula, Dumbbell Nebula, Orion, and many others under dark skies. Scope of delivery: Filter 2″ storage box! Power supply and batteries are not included!