Celestron OIII Narrowband Filter

I have been testing this 2-inch Celestron OIII (oxygen III) narrowband filter, which according to the specifications, isolates 496 nm and 501 nm lines emitted by planetary and emission nebula.

Celestron 93624 OIII filter

The filter looks like a polished mirror that allows some green light that corresponds to the light emitted by emission and planetary nebula to pass through but blocks everything else including most light pollution. It results in enhanced contrast between the sky and the nebula.

An OIII filter reveals an emission nebula in Milky Way’s central region

I have used this filter extensively in visual observation by “blinking” it in and out between the eye and the eyepiece, a technique used in observing emission and planetary nebula. I wanted to know if I could also use this filter to photograph OIII targets with an unmodified DSLR and a telescope and the results look good.

Veil Nebula in OIII, captured with a 4 in f/9 refractor and an unmodified DSLR, 30 minutes single exposure. Image converted to grayscale.

I am only beginning to discover narrowband imaging and I hope to use this OIII filter to photograph targets even in severely light-polluted sky.

To view posts on DIY projects and astronomical equipment, click here.

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

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