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Processing Star Colors LRGB + Narrow Band


(@jeffmorgan)
Main Sequence Star Customer
Joined: 1 year ago
Posts: 51
Topic starter  

I have read that using narrow band filters makes the Adaptive Black Body model problematic.

So would it be possible to get create integrations: One LRGB, one with the NB filter(s), then combine them in the RGB Combine tool after the Star Color Correction has been done?


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(@vincent-mod)
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Joined: 5 years ago
Posts: 5122
 

The correction tool is indeed for broadband data. What does work often is to combine narrowband with RGB, then do the color correction. But also in that case it won't be perfect, closer though.


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(@jeffmorgan)
Main Sequence Star Customer
Joined: 1 year ago
Posts: 51
Topic starter  

With the Good News of Beta 3 being imminent, I have paused processing data except one experiment on Sh 2-101 data. Basically, processed my h-a and LRGB data in parallel and separately as follows:

1) Batch Rotate all integrations;

2) Batch Crop all integrations;

3) Use RBG Combine tool on LRGB integrations;

4) Do Light Pollution Correction on H-a integration;

5) Do Light Pollution Correction on LRGB combined file;

6) Do Star Color Correction on LRGB combined file using Adaptive Black Body model; and

7) Bring the H-a and LRGB files back together using the RGB combine tool. Interestingly, there was no more Luminance channel present.

Unfortunately, the "cure" was worse than disease. All the stars were badly discolored green!


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(@vincent-mod)
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Do you need to do all the rotation and cropping? APP can automatically register all of that together usually. You have a split R, G and B and narrowband data and register them together. Then normalize them and save the normalized frames, which can then be combined. After that I would crop and then try a color correction.


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(@jeffmorgan)
Main Sequence Star Customer
Joined: 1 year ago
Posts: 51
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Yes, cropping needs to be done early because I use an alt-az TTS Panther with an optical tube rotator. The device has limited travel and needs to be reset periodically.

During each reset of the rotator, there is some field rotation that creeps into the next set of subs. And of course, sessions over several nights and filter sequences has potential to add more. So I end up with a pretty wide "spread" of angles centered on my target (see attached screen shot for an extreme example). I suppose this could be countered with a manual adjustment of the camera after resets, but I prefer my sleep so I just let it run all night unattended.

The Batch Rotation is just to get the most favorable angle for cropping given that the Selection Tool is draws horizontal and vertical lines.

Looking forward to seeing Beta 3, will keep your revised procedure in mind for that. To be fair, I have gotten decent results with the current Star Color Correction module using a "light touch", my idea was just to "optimize" it by bringing in the narrow band(s) at a later stage. I just started imaging this summer and I am very much a novice. Especially with the processing!

Field Rotation

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(@vincent-mod)
Universe Admin
Joined: 5 years ago
Posts: 5122
 

Ah I get it, don't know about that device myself, I'll look it up. Alt-Az is a bit of a challenge indeed when doing photography, but it looks like you're managing nicely!

Yes, if you want me to have a look at some of your new final integrations and the color correction on that, no problem, I might see better what a good workflow would be in your case.


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(@vincent-mod)
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Joined: 5 years ago
Posts: 5122
 

Mm, when I look up the mount it says the rotator would allow for equatorial tracking, wouldn't that imply that there shouldn't be much rotation? Or is it that the tube rotates for the guiding to work, but the object then still rotates around... tricky one for me. 🙂


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