NGC281 "the pacman neb " in Ha

[MikeD]

Well most of it.

from last night:

15 @ 10 min's in ha through my 10" newt.

(click to enlarge)

Mike.

[CELESCOPE]

Heck cant believe its come around again, kinda like the way you are getting into these Nebs Mike, something we have not been doing , and seeing different parts of the neb that we have not seen before, excellent detail,

Rog

[FLO]

I reeally like that one 8) The full size image shows a surprising amount of subtle detail.

I'm curious, what is causing the rings around the brighter stars? I actually like them in the same way I do spider diffraction spikes. Am just wondering?

[MikeD]

Cheers guys.

I'm curious, what is causing the rings around the brighter stars? I actually like them in the same way I do spider diffraction spikes. Am just wondering?

I think it is down to reflections between the Ha filter and the cover slip of the CCD chip.

A suggested solution is to increase the distance between the filter and ccd but I have limited focus travel with the newt.

Another solution would be to use a 6/7nm ha filter as I have heard this is much less of a problem with the narrower Ha filter.

Mike.

[centroid]

Nice result Mike, some good detail contained in that one.

I did note, that you hadn't yet resolved the 'halo' problem.

Dave

[FLO]

I had heard that dichroic filters are prone to reflection problems because that is how they work, they reflect unwanted wavelengths rather than absorb them. I dismissed it as one of those problems that didn't matter in the real world, perhaps I was wrong. I doubt that sophisticated filters like the Ha are available in any form other than dichroic but I can at least try a set of LRGB absorptive filters.

[peonic]

Lovely bit of work there Yfronto!

Chris

[MikeD]

I had a go at mellowing the halo's around the brighter stars with photoshop.

They are still there just not so in you're face.

(click to enlarge)

[FLO]

The difference is remarkable 8)

[steppenwolf]

I too wondered about the halos as this was taken with a Newt. but they didn't spoil the excellent image - such depth in there! The 'PhotoShopped' version with the halos removed is even more stunning though. I haven't tried this object yet but am inspired to do so.

With regard to the reflections from the filter, I wonder if you could place the filter in a different part of the light train - maybe just a small movement would resolve the issue?

[MikeD]

With regard to the reflections from the filter, I wonder if you could place the filter in a different part of the light train - maybe just a small movement would resolve the issue?

I think I could, but I want to keep the Ha in the filter wheel .

At the mo I have the cam to filter wheel and filter wheel to scope all as screw fit connections and the only way I can change the distance of the Ha filter to the CCD would mean adding a noise piece to the cam and I am reluctant to do that.

But I may give it a go just to see if it helps.

Mike