Optolong O-III 6.5nm Deep Sky Filter, Unmounted Round Disc with D-31mm

Optolong O-III 6.5nm deep sky filter, 31mm diameter round disk

The OIII CCD 6.5nm Extra Narrow Band Filter is designed for observing nebulae with a bandwidth of only 6.5nm and a central wavelength of 500nm, which corresponds to the emission lines [O III]. Transmission at the other wavelengths is extremely low, particularly those radiating artificial light sources such as mercury vapor and both types of sodium vapor lamps, but also unwanted natural light emitted by neutral oxygen in the atmosphere (brightness of the sky).

O-III emits at 495.9nm and 500.7nm, so the filter appears blue-green when viewed through. Many images of planetary nebulae and supernova remnants were taken with only H-alpha and [O III] filters. They show great structural detail but have natural colors that make them look like an RGB shot.

Unlike H-alpha and [S II], [O III] is very well perceived with the naked eye, which means that this filter can also be used visually.

Main use and properties

♦ Suitable for photographing weak emission nebulae in moonlight or when there is a lot of light pollution

♦ By combining H-alpha, OIII-CCD and SII-CCD, narrowband recordings can be made in the so-called "Hubble palette", such as the famous "Pillars of Creation" (M16, Eagle Nebula).

♦ With the ability to shoot in moonlight and light pollution with line filters, your team won't sit idle for weeks out of the month.

♦ The OIII CCD filter is also suitable for visual observation of most diffuse nebulae, planetary nebulae, and some supernova remnants.