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M31, take 3


tomato
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I promise after this one, not to keep posting Andromeda galaxy images in this section, at least for a while.

This is the outcome of a collaborative project between myself and @Tomatobro, myself providing 125 x 2 mins with the Esprit150/RC571c and 139 x 2 mins with the RASA8/QHY268c and Tomatobro capturing 120 mins LRGB of the core region with his SL RC10/ASI1600. I was concerned that there wouldn't be enough stars in the narrow FOV core region to register and combine with the other, wider images, but APP dealt with the challenge, no problem. The calibrated and stacked image was processed initially in StarTools, including a 0.35x bin factor to produce a 20.5M pixel image. I pushed the detail reveal algorithms in an attempt to accentuate the dust lane detail, especially around the core of the galaxy. Finished in PI (thank goodness for NoiseXterminator) and AP.

I would have like a more 'full bodied' image, to me the galaxy looks a little thin on exposure, but the exercise of combining the data from three different imaging scales has worked out OK, I think.

Thanks for looking.

Image14.thumb.jpg.c6d75f3b11c6d7381c998499001f14fd.jpg

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I don't think any of us has ever taken an M31 with which we remain satisfied for long! :grin: There are so many decisions to make about about dynamic range, colour and local contrasts. 

I understand your desire for a 'fuller body,' though everything is in place here, which is good going for starters. I think several things would help. 1) A higher black point would make the contrast with the galaxy less stark.  That really is a jet black sky and very glossy-smooth. It does looked clipped to my eye though the faint stuff just above it in brightness is there. (The clipped look reduces apparent depth, the argument goes, because it creates a sense of a reflective picture surface which bounces the view back out at the observer rather than drawing them in. I think I buy this idea which I first heard from Dennis Isaacs.

2) It seems colour-cold, to me, meaning a thinner overall look. Warmer colours have more body. The reds are a little acid yellow and the blues a little cyan. A tip towards magenta would, I think, bring more body. 

3) Smaller, softer stars would let the galaxy step forward. By the way, Paul and I did a test run on M31 in the RASA 8 and were knocked out by the result so we're carrying on. I found StarXterminator worked perfectly on the fully stretched image, meaning we could put the stars back at any size we liked.) Small stars bring the gallaxy forward and make it look 'bigger' due to relative scale.

Olly

Edited by ollypenrice
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Thanks for the pointers Olly, StarTools always seems to generate a glossy black clipped sky look, even though I was careful to try and avoid this in the AutoDev stage. 
 

@Sunshine, please let  me try to elaborate on the ‘full bodied’ comment. Visual observers will tell you M31 is the brightest and largest remote galaxy in the Northern sky, and I would like my images of it to reflect this. I think with my eagerness to bring out the dust lane detail, which was after all one of the primary objectives of the project, I have concentrated on this aspect too much, so the exposure and colour balance has suffered as a consequence. I do agree that M31 and M42, although popular beginners imaging targets, present a tricky  processing challenge.

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You really caught a lot of the outer dust but I have to agree with Olly, the sky is a bit too dark the stars are a bit too big. There are also star artifacts. I wonder if StarTools is really doing its job on the stars properly, but I know little about that software. With just the RASA8 data I think you should be able to get better and smaller stars.

 

 

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Here is another version, a bit more full on which is what I was after, I think the dust detail is still there. I confess some of the RASA data was less than brilliant star shape wise, but hey, that's why I keep on imaging it.😉

Image16.thumb.jpg.b0d4d011364788bc8fba04adfa431c83.jpg

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  • 2 weeks later...

Sorry, yet another version, this time with StarXterminator AI 11, which has helped to produce a more realistic (IMHO) foreground star field.

Image12PI.thumb.jpg.c1d8210f8c7d92980e971b029eb82ae6.jpg

 

Edited by tomato
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The first one had the best stars IMO (and overall look, except colourcalibration wise).

All of these look very unnatural to my eyes with mushy and posterized looking stars that are overreduced (looks like star tools took you on a wild ride?). The galaxy itself also looks separated clearly from the background, almost like it was cut out from another image and pasted on this one with unequal levels. the fainter halo shouldnt be all that higher than the background but here it clearly just stops abrubtly and suddenly turns into background. The first image looks good in that way.

Apologies if i critiqued a bit too much, but these are just my 2 cents.

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No need to apologise, they are all valid observations. I see the point about the galaxy halo, this has probably arisen due to my efforts to avoid the StarTools clipped background effect, and as stated previously some of the RASA data used (which provides all of the foreground stars) was of questionable quality.

I think I will have another go at processing but being more selective with the input subs and using APP and PI.

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I use StarTools too and it can give the effect of background clipping. I don’t think it does actually “clip” anything, it just makes the background really dark. I always use the Film Dev module for my second stretch rather than auto dev. There’s a slider at bottom right marked sky glow. Pulling that up to between 3% and 5% gives a more natural background colour. 

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So, yet another version that hasn't been anywhere near StarTools. I culled 67% of the RASA data to get the better star shapes and then processed in APP, PI and AP. I think the stars are cleaner and maybe addressed the 'pasted on' appearance, but colour wise, it looks like the galaxy has been through a mixed wash. I've obviously lost some depth by ditching a lot of the RASA frames. 

Image15a_AP.thumb.jpg.3468b0e29101c292a69237dff650d150.jpg

 

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3 minutes ago, tomato said:

This image is slowly driving me nuts. One more with hopefully most issues addressed at least to some degree, needs more data now...

Image05_APPI.thumb.jpg.33321ead8d421bd28966d455411804bf.jpg

 

This one (and the previous, but especially this one) is excellent, stuff of dreams - excellent.
Background should probably improve a bit if you add more data to it. Maybe it will be excellent^2? Great shot anyway.

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