narrowband filter or o-III

beamer3.6m · (#1 (**permalink**))

Hi

I have the 200p scope and attach me canon 400d to it via an eos t ring thingy which screws onto the 2" eyepiece adapter.

My question is what would be the best filter of the above mentioned in the title or what a normal light pollution filter be better and also what size and how do I fit them.

Also would a filter affect the ability to focus.

Cheers.

roundycat · (#2 (**permalink**))

what exactly is it you want to do?

Dennis

beamer3.6m · (#3 (**permalink**))

DSO imaging of the veil nebula etc etc.

roundycat · (#4 (**permalink**))

Any filter in a converging light path will affect the focus but it will be minimal.

Your title is a bit misleading as narrowband and O3 are essentially the same thing. You can image the Veil and other nebulae in RGB which are wide band filters but can still be effective at cutting out light pollution. Narrowband filters of around 5-12 nanometers usually come in Ha, O3 and S2 flavours for imaging. The Veil gives a splendid response in Ha and O3, others vary quite some.

You will not really need a light pollution filter with any of the above but narrowband are much better at cutting through the murk.

As for size the bigger the better as small filters can cause quite bad vignetting. If your camera has a small chip then 1.25" may well do the job. Position them as close to the chip as possible to minimise the vignette.

If you are new to this I would stay with RGB for a while.

Dennis

Aza · (#5 (**permalink**))

I have the same set up and would recommend the EOS clip in filters.
I use the CLS light pollution filter and also a Ha narrowband filter.
Check out Modern Astronomy - For visual, video and CCD Astronomy for these