[RCC] M42 The Orion Nebula Requests for constructive critique · Omiros Angelidis · ... · 37 · 912 · 9

andrea tasselli:

Omiros Angelidis:
Dear @andrea tasselli Andrea Hello!

I tried less aggressive processing and I would appreciate to hear from you if this is on a better track while I feel that I am not getting the full data of the 7+ hours. 

https://www.astrobin.com/6v61k9/B/

If you want and have the luxury of time I could share you the master light to experiment with. 

PS: I don't have any background on traditional photography and as such I got into a very steep learning curve but I really enjoy every single minute of it. Harsh criticism is only received positively! 

Thanks

Seems significantly improved but there is still room for improvements. Generally speaking you seem to tend to clip the shadows. And some colors seem to be absent or not what I would think they should be. Yes, no problem with processing your master. Just post a link. 

And remember: less is more

Omiros Angelidis:
Here you are Andrea! I am really curious to see what it can be extracted from the stacked file. Thanks a lot for your time. https://www.dropbox.com/scl/fi/yjrl3xtg2x31336sskofy/masterLight_BIN-1_9576x6388_EXPOSURE-180.00s_FILTER-NoFilter_RGB.xisf?rlkey=htcfimrxkiakgccux2bc6a3ci&dl=0

andrea tasselli:

Omiros Angelidis:
Here you are Andrea! I am really curious to see what it can be extracted from the stacked file. Thanks a lot for your time. https://www.dropbox.com/scl/fi/yjrl3xtg2x31336sskofy/masterLight_BIN-1_9576x6388_EXPOSURE-180.00s_FILTER-NoFilter_RGB.xisf?rlkey=htcfimrxkiakgccux2bc6a3ci&dl=0

Hi Omiros,

Just for starters, after having looked at your master, there are two critical things that needs carrying out (which I suspect are part of the issues at large...).

1. It doesn't look it has been flat-fielded too well. Did you calibrate the original lights using a master flat frame?

2. When stacking up it is highly recommended to create (beforehand) and use LocalNormalization files in the stack. Also, CFA drizzle (1x) would help a lot in detail and color rendering. When stacking up use a mid-stack reference frame so that the displacements are equally distributed and the borders of the master frame are rendered much more uniformly, see example below for options:

Can you carry out as discussed so we have a much cleaner master to work with?

Cheers

Andrea

Jon Rista:

Omiros Angelidis:

Jon Rista:

Omiros Angelidis:
For the masters of the acquisition and processing I am seeking their honest feedback, other than the blown out core where I managed to eliminate the trapezium alltogether.

https://www.astrobin.com/6v61k9/

I know that beauty is subjective but I am not seeking a likeable photo. I am seeking a realistic and not overporcessed result, but I always seem to miss that balance!

Thanks you and clear skies!

Omiros

You seem to have a general issue with the final result. I'm curious, what processing did you perform, and how?

Thanks Jon for the generalization and honesty ;)
Here is the processing flow (more or less). 

WBPP stacking
STF preview
Gradient correction 
SPCC
SCNR
Crop
BlurX
NoiseX
Histogram Transformation with EZsuite as I never get a good grasp on the manual mode. I know that this is fundamental but still...
HDRMT to get the trapezium
StarX
To the stars image:
--> Slight saturation bump
--> Slight Deconvolution
Then to the starless image I split RGB
Curves transformation with the same settings to all three channels. Darkening the background and bumping up the brights
Local Histogram Equalization (first pass 32 second pass 128) slight increaments for avoiding oversharpening
Unsharp tool not more than 60-70
Recombination of RGB
SCNR again
NoiseX for another smooth pass with selective range masking to the nebula
Colour saturation
Save as PNG/tiff/xisf 

Thanks

Omiros

So, probably an unpopular opinion...but, I have never cared for what star removal generally does to images. There may be some techniques that avoid the problems I've usually run into (even with say SXT), but I see signs of the same problems in a lot of other images. Since this can be a potentially degrading step, I would maybe try to eliminate it, and skip the RGB star replacement.

I would also probably do your linear processing, then just do a simple HT stretch and just see what you've got at that point. Before doing any post-stretch processing, I would make sure that you are in fact satisfied with your pre-stretch processing. If you are not, then I would keep backing up through your processing history, and adjust the settings of each tool, until you ARE satisfied. Once you are satisfied with your linear processing, I would then try processing the stretched image (which at that point, should be a lot simpler, really.) 

Processing that is often degrading in nature, are the things like star removal, local histogram/local contrast enhancement stuff, SHARPENING (!!!), and improper stretching (can reveal too much noise if its not done right.) 

My experience with NXT, BXT and SXT is more limited, as I just started using them. That said, I've found SXT to generally be destructive to finer details, and haven't yet been able to overcome that (but, its similar to pre-AI techniques, which were also somewhat destructive as well.) I have found that NXT should probably be run FIRST, BEFORE BXT. NXT can soften details, not a lot, but it  can. In contrast, BXT is designed to enhance details. You are probably generally better off running NXT first, then BXT to restore some of the loss in detail caused by NXT. So I would swap the order of those two.

I also find that if NXT is done properly, it shouldn't need to be run more than once, at least not at a high strength. Sometimes I may run a second pass of NXT later in the process just to lightly clean up some of the background nosie revealed by stretching, but if you apply it properly in the first place, that should be less necessary. ACDNR can also be used for that final-pass cleanup, and sometimes it does a better job. You shouldn't need to run SCNR more than once...if you do that properly, you should only need to use curves to manage color, and proper curves application should not introduce any color casts. Some of these things are post-stretch processing, though, and for now, I would avoid post-stretch processing until you are completely satisfied with your pre-stretch processing.

Omiros Angelidis:

Jon Rista:
So, probably an unpopular opinion...but, I have never cared for what star removal generally does to images. There may be some techniques that avoid the problems I've usually run into (even with say SXT), but I see signs of the same problems in a lot of other images. Since this can be a potentially degrading step, I would maybe try to eliminate it, and skip the RGB star replacement.

I would also probably do your linear processing, then just do a simple HT stretch and just see what you've got at that point. Before doing any post-stretch processing, I would make sure that you are in fact satisfied with your pre-stretch processing. If you are not, then I would keep backing up through your processing history, and adjust the settings of each tool, until you ARE satisfied. Once you are satisfied with your linear processing, I would then try processing the stretched image (which at that point, should be a lot simpler, really.) 

Processing that is often degrading in nature, are the things like star removal, local histogram/local contrast enhancement stuff, SHARPENING (!!!), and improper stretching (can reveal too much noise if its not done right.) 

My experience with NXT, BXT and SXT is more limited, as I just started using them. That said, I've found SXT to generally be destructive to finer details, and haven't yet been able to overcome that (but, its similar to pre-AI techniques, which were also somewhat destructive as well.) I have found that NXT should probably be run FIRST, BEFORE BXT. NXT can soften details, not a lot, but it  can. In contrast, BXT is designed to enhance details. You are probably generally better off running NXT first, then BXT to restore some of the loss in detail caused by NXT. So I would swap the order of those two.

I also find that if NXT is done properly, it shouldn't need to be run more than once, at least not at a high strength. Sometimes I may run a second pass of NXT later in the process just to lightly clean up some of the background nosie revealed by stretching, but if you apply it properly in the first place, that should be less necessary. ACDNR can also be used for that final-pass cleanup, and sometimes it does a better job. You shouldn't need to run SCNR more than once...if you do that properly, you should only need to use curves to manage color, and proper curves application should not introduce any color casts. Some of these things are post-stretch processing, though, and for now, I would avoid post-stretch processing until you are completely satisfied with your pre-stretch processing.

Hello Jon! Sorry for not responding earlier! I have missed your response! I will try out your suggestion to leave the HT as the last step of the processing.

andrea tasselli:
With the proviso that it was an "impossible" task given the frames weren't flattened thus giving rise to all sort of gradients (shown as color fringing in the shadows) here the outcome (let's say 1st iteration):

If there is one object LESS suitable for NB imagine I can't think of any.