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Hi everyone. I've recently published a 2-panel mosaic of the Eagle and Swan nebula, capture with my Esprit 100 and ASI 2600MC OSC. I think that for the most part, I like the result. The detail is nice, and 8h plus in each panel meant I could push the stretch without raising too much of the noise level. BXT, NXT and SXT suite also meant I could work well on the details and keep the intensive star field in check. I think, however, that the image lacks a certain "oomph", that is hard to describe. But the image still doens't have that "awesomeness" that I was expecting it to have. I think that one of the reasons is that is that it's too monotone - too much red and not a lot of other colors, specially blue/teal. I know this is a common issue in regular LRGB/OSC images, as Ha pretty much dominante over OIII and other signals. But I wanted some advice on how to stretch the image and get those nice Bluish/purple OIII+Ha signals specially in the center of the nebulae. I know it can be done, as I've seen other RGB images with this profile. Also, I've recently been having issues with Pixinsight after color calibrating, SCNR and stretching (with GHS), I usually get a blue tint in the background which I can't really pinpoint where is coming from.  From Swan to Eagle, a mosaic |
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I have tried a few times doing an Ha Oiii separation at stacking. I know how to do this with APP and Siril but unfortunately not PI. Then you can perform a linear match in PI before combining the channels and process it more like a NB image. I actually have an older OSC image I was going to treat to this process this weekend so I'll post my results and process (if it's any good). I have also had some tints when using GHS. There was an excellent youtube video put out by Paulyman Astro on colour balancing while using GHS stretch. Other than that, I have just tweaked the curves a bit to neutralize out any blue or red tint in the background. |
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Joe Linington: Thanks for the tips! I've done channel separation when using a dual NB filter, in order to get an aproximate HOO image. I've never done it for RGB images, though I supose I could try to stretch the blue channel a little more than the other channels in order to increase the blue? It may not look natural in the end, after all. Guess I could try. As for the videos on GHS, thanks again! Those were very informative. In fact, I noticed I've been using the Symmetry Point feature the wrong way, and that may explain why my RGB channels get so separated after the stretch. |
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Did you use a dual narrowband filter? I only get the blues when using these (L-enhance or Ultimate). If I shoot nebulae in broadband, it is like the other wavelengths interfere with those rich colours. Pinks become brownish and blues become grey. One thing you could try is perform a slight blue S-curve over the nebulae, that should bring the existing blues up a bit. When doing this always try to keep the background the same comparing with the original so you do not bias it. |
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| @Pedro A. Sampaio Have you seen this video? https://www.youtube.com/watch?v=_6in5Kvo95s I think you need to see this also: https://www.youtube.com/watch?v=SQmFFkF6XhM |
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Álvaro Méndez: No, imaged with a clear filter, so it's broadband. Interesting that when I used the IDAS NBZ dual NB filter, I get only red... So I think it really depends on the target. @Pedro A. Sampaio Thanks! I'm watching right now! It seems very useful - Color masking is something I've shied away until now in my processing. Those solutions seem simple enough. And applying that to curves may help to bring those colors back. |
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Thanks to all the tips and several YT videos later, I managed to improve in the colors! I am now much more satisfied with the result! From Swan to Eagle, a mosaic |
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| Yep, definitely looks better. |
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| Phenomenal!! 👏🏻👏🏻 |
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Thanks a lot! I really appreciate it! Turns out I was just stretching the image the wrong way. Just by stretching better and then equalizing the histograms, the color suddenly appeared. A few minor adjustments in curves to balance out the color of the background got rid of the blue cast. I didn't even need to use color masking, though it was good to learn a new technique |
