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HSL Selective Color help


(@tmyers)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 56
Topic starter  

I could really use some help with the HSL Selective Color tool. I am shooting one shot color with an ASI 1600 MC, and I am not certain of the best way to adjust colors.

 

Does using the Red, Yellow, Green, Cyan, Blue, Magenta, actually adjust the RGB channels of an image from a one shot color camera, or should I be using all?

Help me understand the Background selection. I am assuming it is the range of adjustment available on the slider similar to the 3 4 buttons on the right side of the screen. Is that correct?

Also curious about the low high slider and its use.

I have looked for but have not found a tutorial that specifically addressed this tool when using a one shot color camera.


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

If the image is made into RGB then it will work yes, it's a rather subtle tool I always notice.

The background selection defines which range of the histogram is affected by the tool. The first option (0-background) is the noise basically and in there you may want to decrease green a bit and such. I have to admit I haven't used the High and Low slider when using the tool, have to ask Mabula again for that one. 🙂 Will come back to that.


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(@tmyers)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 56
Topic starter  

Vincent,

I am still not sure if I should be trying to adjust the individual R, B, and G channels or just use the All?


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(@tmyers)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 56
Topic starter  

My confusion is this the first image is only 2 hours of data.

 

image

 

The second is with the addition of another 5 hours of data. The 2 hrs looks better than the 7 hrs, and I can get any color to come out on the second one

image

What do you think?


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

Mmm that’s looking a bit strange. Maybe it’s faster if I have a go with the data?

If you can please upload some of the relevant subs to our server;

Go to https://upload.astropixelprocessor.com and use upload1 (or upload2 till 5) as username and password will then be the same as the username.

Create a directory named “tmyers-HSL” and upload in there. Thank you!


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

ps. the High and Low slider refer to the ADU range. So if you just want to affect colors in the high end, you up the low to a higher value and the high to the value above that.


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(@tmyers)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 56
Topic starter  

Vincent,

 

Not certain what you want me to send you. The first image was an integration of 60 x 120s images, the second image is an integration of the original 60 x 120s images plus an additional 125 x 120s images. The 60 and 125 images were taken on different nights.


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

Maybe a subset of both? Like 20 subs of each session with calibration masters?


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(@tmyers)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 56
Topic starter  

OK well I screwed that up royally I made a folder called upload 1 and upload 2, then missed the first folder and copied 23 files to the root directory. I am so sorry


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

😉 No worries I'll put them into a folder and download tonight. Hopefully I'll have had a look then or tomorrow. Thanks for uploading!


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(@tmyers)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 56
Topic starter  

In order for me to have a comparison, I have run what I sent you up to Integration


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

Ok, sorry for the wait. Having a look now.


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

So I think the biggest issue regarding color is that you would need way longer exposure times per light frame. It's very faint and that will impact a good color signal.

So this is one of the datasets (not in upload1 or 2, but what you put in the main server 😉 ). After LP correction;

Screenshot from 2020 08 05 11 57 21

Personally, and these are just 20 frames, I think that already looks quite ok. The data is not great to use with star color calibration, so I'm guessing you used a filter on the camera? If so, you can't use the calibration as it's not broadband data then.

The HSL tool is quite subtle though so that may be why you sometimes don't see a big difference. In the upcoming manual there will be a better explanation. Here's also a bit of info on it: https://www.astropixelprocessor.com/part-6-hsl-selective-color/


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(@tmyers)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 56
Topic starter  

No, no filter used, and you are right Star Calibration took nearly all the color out of the image, but made really nice stars. One day I will move to the dark side and start imaging in Mono and SHO. Expensive switch though.

You mentioned exposure times, all were taken at 120s and the camera was at unity gain. Are you suggesting taking the exposure to 180s or 240s, or to just keep adding frames to the group?

This post was modified 2 years ago by Timothy Myers

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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

Ah no filter, mm, I wouldn't have expected all the color to vanish then. Well, for these kind of objects I would personally (also with color camera's) use narrow-band filters. And then go for exposures of 5-10 maybe even 15 min per sub. It's faint signal and having longer exposures per sub will help getting a nice signal to noise ratio.


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(@ejp2012)
Molecular Cloud Customer
Joined: 1 year ago
Posts: 7
 

Mabula,

Perhaps a video example of this tool is in order. I don't see any difference in the image, except when I adjust the LUM % slider.

I also noticed that in the M20 (Trifid Nebula) video tutorial you adjusted the colors using the tools in the Combine RGB tool, not in the HSL Selective Color tool.

Thanks,

Ed


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(@tsnapp)
Brown Dwarf Customer
Joined: 1 year ago
Posts: 11
 

I would l add my hearty support for this suggestion. It would be a great help for those of us with little experience in dealing with color adjustments to images


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