This Oxygen III Nebular Filter threads into 2" diameter eyepieces and provides a noticeable level of filtration on diffuse and planetary nebulae..
This two inch Celestron Oxygen-III (O-III) nebular filter provides 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.
Wavelength vs. Transmission graph of the Meade Oxygen-III Nebular Filter. The O-III filter transmits high percentages of the Oxygen-III wavelengths while attenuating other undesirable wavelengths.
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.