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RGB Combine tool and pixel math question
@vincent-mod, that does look like a better rendition (image processing being pretty subjective and all), but I do find it a little strange that Sadr is losing it's color. Sadr is a blue supergiant (well, blue/white I guess) and I'd have to go back and run the process again, but just in the normal processing Sadr's blue halo didn't get lost.
I haven't tried APP yet, but PixInsight keeps a stack of the changes made so you can go back through it and the way I use Photoshop, I make a new layer for each change I perform, just so I have that history. I'm wondering if APP has a similar thing and if you can tell in your process steps when the halo became white.
Maybe you just need to process the color image a bit more before blending in the Ha data?
I'm going to download the stacks that Miquel posted here and run it again and check out what's up with Sadr's color.
Hmm. It looks like the color for Sadr is not as much in the color data as I thought it was.
The first image is a quick and dirty process of the color. This is only stretch and saturation, no noise reduction or curves or anything else.
The second is with the ha blended into it 80/20/20, along with then the green reduced a little and a contrast curve applied and a little noise reduction.
This third one is a more proper processing path, still using the 80/20/20 and selective color tricks, but with more proper masking, some sharpening, better noise reduction, at the proper stage and things like that.
Edit: It looks like the upload compression is a little high, so the already compressed JPGs look a bit overcompressed in this forum, introducing some artifacts and smoothing and such. I definitely see the need to compress the images further since it's a forum that will easily fill the server with images, but maybe that can be backed off a little?
Yeah, it lost that blue halo right after me color calibrating the result. According to the graphs, that calibration seems pretty spot on, so I'm now wondering if the emission of that star is less blue than the others? If that makes sense that is, I'm not a astrophysicist. 😉 I'll try another attempt with some extra processing of the separate integrations. Will take a bit as I'm moving to another holiday home at the moment.
Thanks a lot for the sharing of your attempts!
My steps were as follows;
1. Registering the two integrations and saving the resulting registered frames.
2. RGBCombine, where I did the 80-20-20 trick in my latest result
3. In the tools(9) tab I selected "Batch Modify", APP then asks if you want to modify the image which is open in the image viewer. I then draw a box around the area with overlap of both integrations (where they don't overlap, you get that edge which is unavoidable as the frames were not aligned during you taking the picture).
4. I select "Crop ok" on the lower left side and the crop is made.
5. "Calibrate star colors", I select a few areas, usually outside too much nebulosity and go for calibration. You get graphs telling you the before- and after spreads in the various color channels, they should fall close to the predicted model (which is the green line).
6. HSL selective color, I basically did what Neil mentioned in his steps of getting some of the various colours out of their respective channel. It doesn't have a huge effect, not sure why as I never used this tool too much (@mabula-admin ?).
7. I start manipulating the image, I turn saturation on and give a some decent value like 0.35, I then turn the Sat. TH (saturation threshold) down a notch, until I see the background getting saturated which you don't want, so just around the value it doesn't I set that.
8. I up the contrast a bit (CON in the slider) and turn up the sharpening (SHARP). This doesn't affect the stars as they are mostly protected automatically, but can bring out the details in the nebula nicely as you can see if you look at 100% on my latest attempt. The swirls and such are nicely defined.
I think Neil also added some denoise to the mix? I personally tend to not do that (which is where differences in results come from for instance), I just accept the noise as part of the game. 😉 Maybe in the future APP might get a nice one, usually they tend to make details go away a bit.