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M51 - Whirlpool Galaxy

M51 Messier Objects Galaxy Deep Sky NGC5194
Constructive Critique Requested •7 replies•121 views
Paul O’Brien avatar
Paul O’Brien avatar
Hi -  

My second galaxy image in less than a week.  Unfortunately, the Pacific Northwest is not having clear skies.  I'm just getting around to processing some images I never got to.

First, the technical stuff.  Total integration time of 17.3 hours.  254 Astrodon LRGB subs @ 180sec each; 55 3nm Ha Astrodon filter @300sec each at -20C.  Bortle 4 skies near Seattle. 

I think M51 is a very interesting galaxy to process.  I find people tackle this galaxy many different ways; some with a lot of nebulosity and others with more structured arms and core.  I tend to look at the Hubble images of galaxies to get an idea of what they might look like outside the confines of our atmosphere and M51 has quite a bit of Ha along with quite distinct, structured arms.   I tried to hit a happy medium, especially since I had to blend a lot of Ha with the LRGB. Hopefully, I got close.   

The background is darker than I would like.  I used a variety of masks, LHE, HDRMT, noise and color saturation tools before settling on something I liked.  I tend to over saturate and over sharpen images so I tried to consciously be a little more conservative on this front.  

I'd appreciate your thoughts!

Thanks.

Paul

https://www.astrobin.com/fqbep3/
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Uwe Deutermann avatar
Uwe Deutermann avatar
Hi Paul,

this is a tougher one to judge, but expected for M51. I think your arms and detail for the galaxy itself came out super nice! Also the core!! The streams around M51 good to see, not overblown, which you see a lot for this target. Not a fan of the background though, this looks like that too much noise reduction was applied. Or maybe the softening? I would also try to reduce the star sizes a bit more, although less important or impacting the overall image. Also at the top you need a slight more of a crop 😉, now I am going too far … sorry.

Uwe
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Paul O’Brien avatar
Paul O’Brien avatar
Uwe Deutermann:
Hi Paul,

this is a tougher one to judge, but expected for M51. I think your arms and detail for the galaxy itself came out super nice! Also the core!! The streams around M51 good to see, not overblown, which you see a lot for this target. Not a fan of the background though, this looks like that too much noise reduction was applied. Or maybe the softening? I would also try to reduce the star sizes a bit more, although less important or impacting the overall image. Also at the top you need a slight more of a crop 😉, now I am going too far ... sorry.

Uwe

Hi Uwe -

As always, I appreciate your comments.  Too much noise, huh?  Interesting - you might be right.  I used new RC-Astro's NoiseXTerminator and may have used another noise tool during an earlier step in my processing workflow.   I'll check it out.  Funny but Warren mused in our recent tutoring session that he thought NoiseXTerminator might become the standard for noise reduction.  It is a pretty cool tool.  You might want to try it if you haven't done so since it's free right now on a trial basis.  I'm definitely buying it! 

I didn't touch the stars except for putting a small saturation boost early on with an L-Mask.  I protected them pretty much the rest of the way.  Reducing star size in PI is not my forte and perhaps I should learn more about it.  

Take care and thanks again.

Paul
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John Favalessa avatar
John Favalessa avatar
I agree about NoiseXTerminator, it does as good a job as Topaz and very quick…like magic.  It's like a get out of jail card for a noisy image.  My eye doesn't see what Uwe see's as too much noise reduction on the background, but I'm fairly new at this.  I personally think it's a bit too dark.  I'm impressed how you got so dark but still kept the faint trails.  I think this is a really good image overall.  My only comment is I think I'd back the LocalHistogramEq amount a bit (if that's what you used).  Just my personal preference.
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Paul O’Brien avatar
Paul O’Brien avatar
John Favalessa:
I agree about NoiseXTerminator, it does as good a job as Topaz and very quick...like magic.  It's like a get out of jail card for a noisy image.  My eye doesn't see what Uwe see's as too much noise reduction on the background, but I'm fairly new at this.  I personally think it's a bit too dark.  I'm impressed how you got so dark but still kept the faint trails.  I think this is a really good image overall.  My only comment is I think I'd back the LocalHistogramEq amount a bit (if that's what you used).  Just my personal preference.

Hi John -

Thanks for your response.  NoiseXTerminator along with the GAME script have been game (no pun intended) changers for me.   The dedication and innovation by APer's with IT skills is mind boggling to me.  Keep 'em coming, I say! 

After looking back at my workflow on M51, I don't see that noise reduction is particularly overdone but I respect Uwe's interest and thoughtful comments.   I'm always open to other people's analysis cuz that's how I get better, especially given the complexity of PI.  

Yes, the background is too dark and is obscuring some of the fainter nebulosity around the galaxies.  Once I give myself a rest on this target, maybe I'll go back and see if I can fix that issue.  Regarding LHE, I tried to be very careful in applying that tool since it's pretty easy to overdo it if you're not careful.   Maybe I went too far.  Anyway, I appreciate your comments on this one and future images.

Be safe.

CS, Paul
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David Payne avatar
David Payne avatar
Hi Paul,

Excellent image.   I tend to like to see the more of the "atmosphere" around the galaxy.   Before I being processing, I like to see what I had actually captured in my integrated frame(s).   To do this I often over stretch the background - just to see what is there and whether I can use it.  Sometimes, the dim stuff will be overpowered with noise, in which case you forget it or get more subs.   When applying noise reduction, you want to apply enough to get rid of the noise but not destroy the dim signal. 

Of course, I am biased, but I would recommend GHS (if you are using Pixinsight or Siril) which will allow you to really stretch the dims while also being very protective of the galaxy core, which you have already done so well.

Hope this helps,
Dave
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David Payne avatar
David Payne avatar
Hi Paul,

Excellent image.   I tend to like to see the more of the "atmosphere" around the galaxy.   Before I being processing, I like to see what I had actually captured in my integrated frame(s).   To do this I often over stretch the background - just to see what is there and whether I can use it.  Sometimes, the dim stuff will be overpowered with noise, in which case you forget it or get more subs.   When applying noise reduction, you want to apply enough to get rid of the noise but not destroy the dim signal. 

Of course, I am biased, but I would recommend GHS (if you are using Pixinsight or Siril) which will allow you to really stretch the dims while also being very protective of the galaxy core, which you have already done so well.

Hope this helps,
Dave
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Paul O’Brien avatar
Paul O’Brien avatar
Hi Dave -  

Sorry for the long delay in responding but life has gotten in the way.  smile  Thanks much for your positive feedback!  

I also appreciate your specific suggestions about processing the galaxy.  I've tried your technique of overstretching the background a few times but not many so I'll have to give that a shot more often and see what happens.   I do use PI so I'll look into GHS, which sounds like a very useful tool.  

Thanks again!

Paul
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