M45 reprocess, star halo issue

[upahill]

Had another go at processing the M45 data last night. One thing really bugging me is the halos around the larger stars. I am assuming these are caused by the UHC-S filter in the T-ring adapter but cant work out if the fact they are not concentric throughout the field is indicative of filter alignment, or just normal.

Eitherway I think im going to move on from M45 until I get a bit better at processing, it seems very difficult to bring out the detail without super long exposures.

[x6gas]

Hmmmm.

I'm not that familiar with the UHC filter but it appears that it is really designed for emission nebulae whereas M45 is a reflection nebula.  I think you'll be cutting out a lot of whispy blue haze in this target if (as I suspect) the filter is only passing the blues from the OIII wavelength.

Anyway, I had a very similar issue with haloes on the same target way back when:  

You'll see speculation on what was causing the haloes in thread but it was definitely something to do with the Baader filters as the problem went away when I switched to Astrodons.  That's not to say it's definitely the filters alone as there may have been some kind of interplay with something else in the imaging train.  I don't recall ever having had a similar issue on any other target... but then I don't recall imaging anything else with such bright, blue stars.

It might help if you could list out exactly what kit you were using...

Cheers, Ian