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Walking on the Moon

M31 with more data and some help please.


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I've added some more data to my Andromeda and i think the shot is improved in colour and detail. I'm still very much a newbie with PI and I noticed an issue with the stars which I don't understand. If you look closely at some of the bigger ones (and smaller) it almost looks as if they haven't aligned properly and there's a small circle attached to them? Can anyone offer some advice please? I use staralignment and batchpreprocessing in Pi.

Thanks Steve



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I very much doubt that it's focus. I'd say it's an alignment/stacking problem with the blue channel. It only applies to the left hand side of the image. If the blue channel were soft in focus then you'd expect blue bloat fairly evenly around the stars. What we see here is a big bite out of the left hand stars where the colour combination hasn't worked. Did you run any hot pixel filtration in the stacking? This can attack stellar cores thining they are hot pixels.

If you'd like to put a Dropbox link with your three channels I'd be happy to try the Trichromy combination in AstroArt for you over the weekend.


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There are several stacking artefacts in this image. Thre are lines going from top to bottom, and on the right hand side there is an edge from a rotated sub. In this area, the issue you have with the stars seems reversed.

You could try to redo the alignment of all the subs using the StarAlignment tool.

You can also do a new alignment on the master frames, before combining them.

Just a thought.

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I've had a go at using staralignment but its not made any difference. Interestingly, I have reprocessed the R channel in DSS and it looks much better. I've attached the DSS processed version (ignore the processing i haven't tried to make it look proper). This seems much better in terms of the star issue????


Edited by steviemac500
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