Meade Oxygen III filter - 1-1/4" threaded cell
This filter passes the Oxygen III emission line while blocking other wavelengths for imaging or visual observing.
From the Meade web site:
Meade Oxygen-III (O-III) nebular filters provide an extraordinary level of nebular filtration on diffuse and planetary nebulae. Observations of these nebulae in a city environment with the O-III filter often yield more image contrast than observations of the same objects in a dark-sky setting without the filter.
The O-III filter extracts more than 80% of the light emanating from the two oxygen-III spectral lines at 496 and 501nm. Objects such as the Omega (Swan) Nebula (M17) in Sagittarius, the Orion Nebula (M42) in Orion, the Helix Nebula (NGC 7293) in Aquarius, and the Eagle Nebula (M16) in Serpens are revealed in dramatically increased detail. Meade 60-layer interference coating technology isolates the desirable O-III lines, while attenuating other spectral lines virtually to zero.
Excellent condition, no scratches or blemishes.