Pacman with annoying artefacts

[Erling G-P]

Had a go at The Pacman Nebula (NGC 281) last night.  Happy with the result, apart from a very annoying horisontal set of stripes on the left, and a fainter, vertical one on the right.  Never seen this before; seems the horisontal one might stem from the bright star in the nebula, but can't see an obvious source for the vertical one.  Have tried to remove them with countless iterations of 'Remove line' in Astroart, but have only succeeded in reducing them.  Would probably have to paint them out pixel by pixel to get completely rid of them.  The one where I've tried to remove them, has been treated with Topaz DeNoise and an unsharp mask in Astroart.

84 x 180 sec subs = 252 minutes total.

SW 200PDS, HEQ5Pro / Rowan belt mod, SW 0.9 CC, Canon 700Da cooled, Staraid Revolution autoguider, darks, flats & bias.

[almcl]

I think they may be caused by diffractionspikes/reflections from Shedar (Alpha Cas)  and Achird (Eta Cas).  Something in your imaging train (Skywatcher's Coma corrector is one possibility) may be picking up on these.

Here's your image overlaid on the surrounding area and the directions of the stars and the strength of the spikes is quite persuasive:

Edited August 16, 2020 by almcl

[Erling G-P]

58 minutes ago, almcl said:

I think they may be caused by diffractionspikes/reflections from Shedar (Alpha Cas)  and Achird (Eta Cas).  Something in your imaging train (Skywatcher's Coma corrector is one possibility) may be picking up on these.

Here's your image overlaid on the surrounding area and the directions of the stars and the strength of the spikes is quite persuasive:

Thanks fot that analysis; it's very interesting.  Quite remarkable if these two stars can have such an impact, considering how far outside the view they are.

[michael8554]

Given the very oblique nature of the reflections, a Dew Shield might help.

Michael

[Erling G-P]

2 minutes ago, michael8554 said:

Given the very oblique nature of the reflections, a Dew Shield might help.

Michael

Thanks, I already have a large one on it

[MarkAR]

A good image, just a shame about the outlying spikes.