Hb + Unmodded Cam versus Ha + Modded Cam

[Ags]

So Agnes, from my point of view it's a good thread but doesn't answer. " Is Hb affected by the moon like O111 ? "

I think the answer to that lies in the nature of OIII - OIII is comprised of two emission lines so there is a limit to how narrow an OIII filter can be (501 and 496nm) - allowing for 3nm either side of the two spikes we get a 'minimum' passband of 11nm. Hb is one line so the filter can go narrower and cut out more moonlight.

For example, Astronomik make a 12nm OIII, which would let through twice as much moon as a 6nm Ha.

[Ags]

My last go on M42 and surrounding area was much the same but with 33% Ha in the blue - I may try it with less Ha.

Making Every Photon Count gives a few recipes.

If you really want to simulate the visual experience, map Ha to 33% Blue and 33% Green, and OIII to 67% Green... 0% of anything to Red - the eye can't see Ha red at night :-)

[Gina]

I have a 3nm OIII but haven't used it with moonlight yet. I'll be interested to see how it performs and if was worth the cost It certainly works well without the moon - nice tight stars

[Gina]

Making Every Photon Count gives a few recipes.

If you really want to simulate the visual experience, map Ha to 33% Blue and 33% Green, and OIII to 67% Green. )% of anything to Red - the eye can't see Ha red at night :-)

Thanks Must have another read of the "imaging bible"

[Ags]

3nm OIII

I gues it only lets the main line through? What filter is that and did it cost a fortune?

[Gina]

It's an Astrodon 1.25" 3nm OIII filter bought from Ian King. Yes, quite a pricey £359. Rather a lot for a little piece of glass in a holder

[davew]

Astrodon use 501nm. 5 is better than 8 but 3 is better then 5 pass band. 5 is still affected by the moon.

For a true experience, process as normal then move the white point to the left as far as it'll go to leave one or two white dots on the image. Then coat liberally in orange !

Dave.