[RCC] DSO processing workflow - am I going in the right direction? (here M42)

Hi,

I can't guide you about the tools because I don't use Siril/Gimp for processing but I can enumerate some aspect that you may want to improve.

-The star shapes are not round and the overall image is a bit blurry. Seems like the focus is off.

​​​​​​-The color balance seems a little off too. look at the brightest blue stars, they are a bit green near the core (for my taste).

-The core is clipped. You probably need to take shorten exposures.

-The background is too dark. Again, this is a personal preference. I prefer to keep the "true black" of the image at a brightness not less that 0.1 (for a 0 to 1 range).

-The transition from the background to the dimmest nebula features has "holes". This can happen if you pushed up the brightness using a mask that is too noisy. Don't know if it is the case…

Hope it helps!

Everything Alberto says is spot on - wanted to add (and it is something I am still working on) - is that you can take multiple exposure sets, for example: 40 x 120s and then do 20 x 10s and blend the two together, especially at the core of m42, to get a less blown out look. The issue I have personally is that all my longer exposures of Orion are too long to get a good blend. I am not sure how to do that in Gimp, but if it works similarly to Photoshop it can be done.

Beyond the over-blown core, the main issue I see is the focus. Everything else can be fixed with processing.

Great, it seems I have material to work on! I appreciate all you comments

Focus: That's an interesting comment. Probably I have been convincing myself to have focused correctly from what I was seen in 3" display of the DSLR, and always blamed the lens quality
I will do more tests to see how much I can improve in this respect

Saturated core: That's true... I should have cared more. Noted!

Star shape and color: Perhaps, the asymmetry in the star shapes is due to the extensible part of the zoom lens which is a bit wobbly... that's my guess.
Moreover, the same star has a different shape in each channel... not sure how to fix it, apart from upgrading the gear

Background, sharpness and holes: I see what you mean, I'll try to improve over them.
About the holes, actually there are no masks involved. I'd say it's the combination denoise + local contrast pushed to much...

Thank you all! also for the encouraging words, Olaf and Jared
Daniele

Alberto Ibañez:
For focus, I suggest you to use a bahtinov mask. Works great and it's very easy to make it with a piece of black cardboard.

The point is that I am already using one

Anyways, last night I made a third attempt to keep the processing defects and artifacts under control.
I kind of set this @Jared Holloway 's picture as target, which I like

- I made sure the background was not clipped and made it a little bit brighter (gimp says median is around 1% of the range, but at 10% of the "perceptual space", not sure that is what you meant Alberto)
- I set a white reference to fix the previous cyan halos around the brighter stars, and the overall tint has shifted quite a bit. But there are still some grayish halos that I wasn't able to deal with
- not sure it matters with the sort of "washed out look", but I haven't mentioned that it's a 50% crop in height and width of the original pic.

Thanks again!

Jared Holloway:

Anyways, last night I made a third attempt to keep the processing defects and artifacts under control.
I kind of set this @Jared Holloway 's picture as target, which I like

Thank you! This process looks good (in my opinion!) - m42, as I mentioned before, is still a work in progress for me - mainly for the core and its brightness. I think with m42, in many respects its personal preference on how bright / blown out you want the core - some people like it not bright at all, some like it bright. I am an in between person, I like it sort of bright but with still being able to see the Trapezium.

For the trapezium you need a very short exposure time. So M42 is a blend, no single malt. ;-)

Very nice image, be proud of what you do as WE ALL are learning in this whole world of processing images!

I’m far from an expert and pretty much everything mentioned about over exposure of the center/core is the biggest thing I see.  Would definitely shorten exposure time. I always have that problem myself! 

I’m a really big fan of Gimp and I use it for most of my post processing and LOVE the G’mic plugin! Just a couple of things I have found to work well for me in other images is the “JPEG Smooth” filter and there is a wavelets filter that I’ve found to work quite well to help smooth the image before any sharpening that I do. I’ll usually do the Wavelet thing 2 times maybe 3 if it looks like its working. 

As far as sharpening goes, there is another plugin that I found called Py-Astro and its got a few sharpening options that I really like and use over the normal “Unsharp Mask” called “SMART SHARPEN” 

I don’t now if this is a standard practice or not but when ever I am in GIMP and do something specific I like to make a duplicate layer and use the “Opacity” in the layers window. I especially do that for the “Star Reduction” and “Sharpening” that way if I think I may have over done a process I can easily back the process off or tweak the strength of it. Again I really like that for the Star Reduction.

Again I’m not an expert thats for sure but I do love Gimp and found it to be a really solid tool for someone that doesn’t like subscription based softwares.

Keep up the great work!

Dale