Alcyone - something a bit different and some help please! Taken at full moon... (Simon)

Celestial hemisphere: Northern · Constellation: Taurus (Tau) · Contains: 24 Tau · 25 Tau) · 25 eta Tau · Alcyone · HD23511 · HD23584 · HD23585 · HD23607 · HD23631 · HD23632 · HD23642 · HD23713 · HD23733 · HD23763 · HD282967 · HD282970 · HD282973 · M 45 · Pleiades · The star Alcyone (η Tau

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Alcyone - something a bit different and some help please! Taken at full moon...

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Alcyone - something a bit different and some help please! Taken at full moon...

I have long had a concern about the shapes of my stars on the peripherals of my images when using the Classic Cassegrain. There often appears to be a lot of coma, too. This seemed odd, as that is normally the case for fast scopes, not f12s! Having got in touch with a specialist, it appears as though the primary mirror itself, runs at probably f3 hence the coma, and of course this scope is not really meant for the imaging I am forcing it to do! So, I suggested a coma corrector and to use that with the 0.75% reducer I have for the scope, which makes it run at f9 and my preference. The specialist felt it was unlikely to work - but as you can see I think, all things being equal, the stars are pretty good.

However, when I tried this last night with a Ha filter, I could not reproduce this result. I fiddled around for ages in -2C temperature but could not repeat what I got here, and what I got for my M46 too - the next one posted. So, it seems to work for a UV-IR filter, but not Ha - it does not seem to make any sense to me. I just think I got lucky, and it all seems a bit hit and miss to me. So, has anyone got any ideas how to get my scope running at f9, with less peripheral star issues please. I would even accept a post-processing method if there is one - although fixing the source issue would be best.

Anyway, I took this image whilst it was a full moon, hence the lack of nebulosity, because I could 'waste' the night if you see what I mean. It was a nightmare to process too, because of the gradients etc. This was 130 subs at 1 minute long each. This equates to 2 hours 10 minutes. Thanks everyone for your support...

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Status	Advanced success
Started	...
Astrometry.net job	7134099
PixInsight job	5VKAI2A8UD1RQAW08W3WWQNLKBFJWTQC
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	03h47m26s.666
RA (top/left)	03h48m13s.410
RA (top/right)	03h48m32s.807
RA (bottom/right)	03h46m39s.986
RA (bottom/left)	03h46m20s.840

Dec (center)	+24°06′37″.63
Dec (top/left)	+23°46′14″.58
Dec (top/right)	+24°24′01″.30
Dec (bottom/right)	+24°27′02″.89
Dec (bottom/left)	+23°49′14″.62

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Alcyone - something a bit different and some help please! Taken at full moon...

Alcyone - something a bit different and some help please! Taken at full moon...

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Alcyone - something a bit different and some help please! Taken at full moon...

Alcyone - something a bit different and some help please! Taken at full moon...

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