For extreme contrast enhancement when observing nebulae

The O-III filter is 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 than a UHC filter or no filter.

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

Baader [O III] filter transmission curve

The transmission curve shows a small 10 nm FWHM band - exactly on the [O III] line at 501 nm.

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.

Specifications:

• Plane-optically polished surfaces
• Hard-multicoated
• 10 nm FWHM band on the [O III] line at 501 nm
• 1.25" filter thread
• Aluminum cell
• Knurled edge
• Substrate 2 mm thick

Scope of delivery:

• Filter in plastic box