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M31 - Revisit


gnomus

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One of the first targets I went for when getting into the AP malarkey was, naturally, M31.  I thought that it might be time to revisit the scene of my earlier crime: https://stargazerslounge.com/topic/256542-m31-reprocess-from-mid-september-2015/

This was taken over three nights at the end of November.  The ED80 has been swapped out for a WO Star 71 (Mk I) and I used a Moravian G2-8300 in place of the Atik 383 on the earlier effort (same chip, of course).  This time around I tried not to go too overboard with the stretch or with the saturation.

Data:

Baader Blue 36 mm: 16x300"
Baader Green 36 mm: 16x300"
Baader Luminance 36 mm: 61x300"
Baader Red 36 mm: 16x300"
Chroma Ha 3nm: 6x1200"

All unbinned for a total integration time of 11 hours and 5 minutes.

Thanks to @ollypenrice and to @Patrick Gilliland for some early tips on the processing of some issues with this.

HaLRGB_PBx1920px.jpg

Edited by gnomus
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Thanks everyone for your encouraging words.

2 hours ago, red dwalf said:

love it, can you tell us how you went about processing this, i`m struggling big time with the light pollution and gradients the poor seeing gives me which also tends to ruin the colours somewhat.

I don't know if I am expert enough to comment, but I can tell you what I do.  Firstly, I have stopped attempting to image when the conditions are not conducive.  I used to pay little heed to the Moon, for example, believing that if I pointed my scope at something on the other side of the sky I would get away with it.  I didn't.  Processing was a nightmare and the results were poor.  Secondly, I tried to be rigorous as to the level of LP I would 'accept'.  I am semi-rural and am pretty fortunate sky-wise.  However there are a couple of areas where LP starts to come into play in a significant way.  So I will stop capturing data when the scope gets round to those areas (I use SGP's plate solving feature, so I can always quickly start on a second target in a 'good' part of the sky if the mood takes me - or I could just go to bed early!)  Most of the M31 LRGB was shot when M31 was high in the sky.  I don't use a LP filter in my imaging train, but I am aware that some folks do do this (that is, they have the light coming through scope, then their LP filter, and finally through their 'imaging' filter.  That might help if you have a significant problem.  

Even with these measures I still require DBE: the RGB I DBEd twice (though I am not sure it needed the second round). 

1 hour ago, SkyBound said:

Any reason what you swapped out your Atik 383 for the Moravian... ..?

i thought you were very happy with the Atik...? :)

OK - you have induced some PTSD.  I haven't ditched the Atik, I still have it.  In the spring it looked like I might be able to source a second WO Star 71.  I thought I could put together a dual WO Star 71 rig (a sort of poor man's version of Olly's dual Tak set up which I had, at the time, just recently played with).  A dual rig means a second camera, of course, hence the Moravian.  (I was going to use the integrated OAG on the Moravian to guide).  However, these plans came to naught when the second WO Star 71 that was delivered turned out to be no good.  I haven't yet decided what to do with the perfectly good Atik 383 that I have.  I will probably sell it in the new year.

2 hours ago, ollypenrice said:

Very, very nice natural and unforced Andromeda. The speckling of Ha is just right for me. I might take a point off the black end (which I very rarely say) but a lighter sky is also good. This wpuld print well.

Olly

Thank you for commenting Olly.  I have had a go at taking 2 points off the black and it does look a little better.  The difference is subtle though, and I don't think it merits a repost.  My dream is that one day I will manage to post an image thread that doesn't have 4, 5 or even 6 different re-works. :icon_geek: 

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3 hours ago, gnomus said:

 My dream is that one day I will manage to post an image thread that doesn't have 4, 5 or even 6 different re-works. :icon_geek: 

I used to have the same dream but now I realise that it will never happen...

(I just leave a year or two between reworks on the grounds that I've added another night's worth of data. Don't tell anybody.)

Olly

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Skillfully done Steve, very natural with understated colours.  You know it's good when it doesn't look processed :icon_biggrin:.

Reprocessing old data is a satisfying method to confirm progress in applying all those techniques.  However, I'm sure we would prefer endless clear skies to gather new data . . .

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5 hours ago, gnomus said:

I don't know if I am expert enough to comment, but I can tell you what I do.  Firstly, I have stopped attempting to image when the conditions are not conducive.  I used to pay little heed to the Moon, for example, believing that if I pointed my scope at something on the other side of the sky I would get away with it.  I didn't.  Processing was a nightmare and the results were poor.  Secondly, I tried to be rigorous as to the level of LP I would 'accept'.  I am semi-rural and am pretty fortunate sky-wise.  However there are a couple of areas where LP starts to come into play in a significant way.  So I will stop capturing data when the scope gets round to those areas (I use SGP's plate solving feature, so I can always quickly start on a second target in a 'good' part of the sky if the mood takes me - or I could just go to bed early!)  Most of the M31 LRGB was shot when M31 was high in the sky.  I don't use a LP filter in my imaging train, but I am aware that some folks do do this (that is, they have the light coming through scope, then their LP filter, and finally through their 'imaging' filter.  That might help if you have a significant problem.

That all sounds like really good advice to go along with a wonderful image. What a difference 2 years makes. 

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13 hours ago, gnomus said:

..... My dream is that one day I will manage to post an image thread that doesn't have 4, 5 or even 6 different re-works. :icon_geek: 

But not this time.  I have taken the black point in as per Olly's suggestion.  I did another run of LCE for the dust lanes only.  I did some minor work on star haloes:

HaLRGB_PFx1920.jpg

Edited by gnomus
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