O-III filter especially useful for planetary nebulae. In the O[III] line, they show their most interesting structures. But O[III] regions are also embedded in other gas nebulae. So an O[III] filter can show completely different details as an UHC filter or no filter.

The Baader O[III] filter is very narrow banded with only 10 nm FWHM. We recommend it for apterures above 200mm. It is a good addition to the broad band UHC-S filter from Baader.

With the O[III] filter, even under worse stray light conditions in big cities, successful observations are possible. The background remains black also at big exit pupils.

The filter is dielectrically coated and aging-resistant, robust and scratch-proof. Highest image quality is guaranteed by plane-optically polished surfaces.