M 81 and M 82

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decay
Posts: 433
Joined: Sat Apr 10, 2021 12:28 pm
Location: Germany, NRW

Re: M 81 and M 82

Post by decay »

Hi Mike!
Mike in Rancho wrote: Tue May 10, 2022 6:30 am And when I use it for DSLR files I actually also use the AstroSimple interpolation algorithm.
I rebuilt the ASTAP stack with AstroSimple interpolation and replayed the ST session with Guy's nice STReplay tool. The outcome seems to be a nearly perfect copy of the first one:
astap_diff_astrosimple.png
astap_diff_astrosimple.png (498.38 KiB) Viewed 2342 times
Maybe the dataset must have special characteristics to take advantage of AstroSimple interpolation :think: ?

Best regards, Dietmar.
Mike in Rancho
Posts: 1141
Joined: Sun Jun 20, 2021 10:05 pm
Location: Alta Loma, CA

Re: M 81 and M 82

Post by Mike in Rancho »

Hi Dietmar,

Yes those do look very close, if not identical. I also have to say that I didn't do any comparison testing of ASTAP's own bilinear vs the AstroSimple, just DSS bilinear, DSS superpixel, and DSS Bayer drizzle, vs AstroSimple. The ASTAP version won, but maybe it was more of the stacking alignment (or other factors) than the debayer algorithm itself. :think: More testing would be needed...but I am testing out so many other things right now that it'll probably be on the back burner for me.

Another thing to think about with the "#2" style of comparisons -- it tends to be hard to match-process different files in ST, because many of ST's features are dynamic to the data itself. So it's not like you can just pick the same settings, you can really only eyeball it as you go. Best really to try it side-by-side on different computers at each step. Yep, I've done that. :lol:
decay
Posts: 433
Joined: Sat Apr 10, 2021 12:28 pm
Location: Germany, NRW

Re: M 81 and M 82

Post by decay »

Hi Stefan, Hi Mike,

I still owe you (both) some feedback to tips and hints you gave me but I missed to reply to. Tomorrow is a very sad day here for me: Astronomical darkness will vanish for the next two months. But that gives me the opportunity to reflect our discussion and work up some things. :)
Please note, there's no need for you to reply (unless I have a new question :lol: ). I just would like to underline that I followed every post.

I will start with the oldest relevant post, in this case from Mike:
Mike in Rancho wrote: Fri May 06, 2022 7:45 am The new HDR should be both more capable and produce better all-around images than old-HDR, but may take a bit of practice. Some of the stuff buried in the previous preset algorithm choices are now within our control. Probably the most common issue is how to get something like "reveal core" in 1.8 (an important thing in galaxy season!), which can be done with a low context and increased shadow on the left-side sliders.

In SS, occasionally Strength can have a counterintuitive result. I more often adjust the gamma to moderate the effects of DimSmall and Isolate. Usually Isolate, as .50 is pretty heavy. DimSmall used to have a default setting of .50 but is now .75 and I often leave it alone.

For a post-tracking FilmDev, note that there are likely default settings in the Dark Anomaly that probably cause that minor initial effect, even without starting to change the other controls. I will sometimes drop the gamma also, which can help suppress a dirty sky and also increases the contrasty appearance. That can be balanced off with Skyglow, if desired. Every image may need a little something different to show what it is you want to show.

Intended display matters too. I've realized I usually have to make those final adjustments to make a (darker) version for my phone, even when the original may look great on a calibrated computer monitor. Probably because the phone has a jacked-up gamma that I am counteracting?
Regarding HDR: You were right: The main point differing from the pre 1.8 versions was/is the context size and meanwhile I read Guy's HDR Module Use (v1.8) and this was very helpful. This post processing of M81/82 was my first try with the ST 1.8 version and obviously it would have been better to read the new documentation beforehand ...

With SuperStructure I have sometimes better results using the Strength parameter, as Stefan did. Gamma sometimes tends to leave ugly mottles, but I guess, I simply have to practice a bit more to get it right ...

Post-tracking FilmDev: Your hint first dropping gamma and then balancing off with Skyglow, to suppress a "dirty sky" will surely help me to get some images more convenient. I reworked an (partly failed) image of M96 / M105 to practice and this technique looks pretty promising.

Intended display: Absolutely right! I use an old tablet as digital picture frame for my AP images and it is very annoying that the images are always looking too bright with ugly mottling in background :evil: . But as there's no way to calibrate this display the only solution is to create extra images with proper adjustments. :cry:

Best regards, Dietmar.
Stefan B
Posts: 422
Joined: Sat Oct 31, 2020 8:59 pm

Re: M 81 and M 82

Post by Stefan B »

Inspired by Freddy's M81/M82 thread (viewtopic.php?f=10&t=2802) I played around with ST1.9 alpha. I guess gradient treatment is a bit better and also the Ha inclusion in M82. Silly me, I wasn't aware of how important the detail size slider is... Great to know now.

Image
fmeireso
Posts: 367
Joined: Mon Sep 28, 2020 8:46 pm
Location: Belgium

Re: M 81 and M 82

Post by fmeireso »

Great image Stefan! :thumbsup:

I think imho v 1.9 is so much better for Nbaccent then fhe former version; Of course i noticed on Astrobin you have quite some time put in.
Anyhow, your m82 looks great..i decided for myself to more data in...i am conviced in my case i can get more Ha data out if i take some more integration time.
Not this week, too much bad weather now, and next week i am off to Spain for several days...so hopefully by the end of March...we will see...
Stefan B
Posts: 422
Joined: Sat Oct 31, 2020 8:59 pm

Re: M 81 and M 82

Post by Stefan B »

Thanks, Freddy. Yes, I invested quite some time. And time always helps, right? Although in this case 20h would probably have done job. Wishing you good luck with adding more time to your project!

Regards
Stefan
Mike in Rancho
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Joined: Sun Jun 20, 2021 10:05 pm
Location: Alta Loma, CA

Re: M 81 and M 82

Post by Mike in Rancho »

Very good, Stefan. :thumbsup:

The background, shapes I guess, match up quite nicely with references to the IFN of the region. Hard to pick up!

The M82 came out well, better than mine did. I think my 1 hour of Ha was insufficient for clean data there, and I also managed to induce a gradient in my NB file - maybe something I did in Wipe - that made it even more difficult. I am pleased that some of the "burst" shape is similar to what you are showing here, though I had a ton of scattered noise about it.

The M81 looks good but could be showing some pink donutting of continuum Ha towards the core. I had a difficult time with the reversal on that, trying to decide what was a real knot of Ha and what was just generalized brightness. Altering detail size and brightness correlation from the Galaxy defaults can help, but in my case only so much.

Some of that may be because the Ha accenting here is a bit different all in one image. M81 wants typical galaxy arm little Ha blobs, yet M82 wants an extended bilateral burst of larger feature size. Thus, things like detail size and bright correlation aren't identical between the two.

Or so I theorize... :confusion-shrug:

Stars look good. :bow-yellow: Am I the only one struggling with the SVD since the deringing change? Maintaining resolution can help me somewhat, but as seen in another recent thread binning can be required or the sampling doesn't work. Tough balance. I still have to run back to 536 most of the time, though I am becoming a little better with ringing repair in Shrink.
Stefan B
Posts: 422
Joined: Sat Oct 31, 2020 8:59 pm

Re: M 81 and M 82

Post by Stefan B »

Thanks, Mike!
Mike in Rancho wrote: Thu Mar 09, 2023 6:20 pm The background, shapes I guess, match up quite nicely with references to the IFN of the region. Hard to pick up!
When you look at my first try, you see that there much of the "IFN" is in the lower left. That didn't match with most of the images I saw. So it was quite sure that much of this was gradient instead of IFN. On the other hand it was hard to settle on the correct wipe settings since the shape of the IFN changed depending on the aggressiveness. So I turned to some images taken from the desert...there shouldn't be any gradient, right? ;)
Mike in Rancho wrote: Thu Mar 09, 2023 6:20 pm The M81 looks good but could be showing some pink donutting of continuum Ha towards the core. I had a difficult time with the reversal on that, trying to decide what was a real knot of Ha and what was just generalized brightness. Altering detail size and brightness correlation from the Galaxy defaults can help, but in my case only so much.
100% agreement on the continuum Ha in M 81. But I didn't know what was knots and what was stars which were picked up and colored pink. I didn't selectively reverse any knots in M 81 since I wasn't sure about it so I left it.
Mike in Rancho wrote: Thu Mar 09, 2023 6:20 pm Some of that may be because the Ha accenting here is a bit different all in one image. M81 wants typical galaxy arm little Ha blobs, yet M82 wants an extended bilateral burst of larger feature size. Thus, things like detail size and bright correlation aren't identical between the two.
Again agreement :) I actually did two runs of NBAccent for this image. One for M 82 with parameters rather suited for nebulae and one for M 81 rather with the galaxy preset. M 82 shows basically Ha on it's own without broadband signal/luminance being there to be accented. So brightness correlation doesn't to the job.
Mike in Rancho wrote: Thu Mar 09, 2023 6:20 pm Or so I theorize... :confusion-shrug:
So do I :D
Mike in Rancho wrote: Thu Mar 09, 2023 6:20 pm Stars look good. :bow-yellow: Am I the only one struggling with the SVD since the deringing change? Maintaining resolution can help me somewhat, but as seen in another recent thread binning can be required or the sampling doesn't work.
Didn't have problems with sampling (binning was 60% or so). But I had to bump up deringing quite a bit.

Regards
Stefan
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