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2022-05-29: APP 2.0.0-beta2 has been released !

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windows 2.0.0-beta2

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ASI183MC pro Bayer pattern question


(@mkeller0815)
White Dwarf Customer
Joined: 2 years ago
Posts: 22
Topic starter  

I’m using a ASI183MC pro camera for capturing images. Capture software used is astroberry and the Images are saved as FITS. The FITS header state RGGB as Bayer pattern and APP is set to use the pattern in the header.
I would expect the images to be more green, because of the two green pixels compared to only one pixel for blue and red. But the image is more blue (single image, auto stretched). So I’m not sure if the color channels are swapped in a way and if I force any other Bayer pattern it comes out even stranger. If I set BGGR then the image is more red what is expected, because just red and blue are swapped out.
Any ideas on that? I can provide a sample image if needed.
Mario.


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1723
 

@mkeller0815 Hi Mario, yes please provide a few example files. You can login to

https://upload.astropixelprocessor.com/

using upload4 as both username and password and create a directory called mkeller0815_bayer and put the files in there. Then I will have a look as soon as you have uploaded them.


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(@mkeller0815)
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Joined: 2 years ago
Posts: 22
Topic starter  

@wvreeven thanks for the quick reply. I uploaded two light frames from two different sessions and targets. Let's see what you can find. FITS header looks okay to me but I'm not sure if there should be some color correction values like we have in other RAW formats. 


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(@wvreeven)
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Joined: 4 years ago
Posts: 1723
 

@mkeller0815 Thanks very much. Can you upload a few examples of normal frames as well for comparison?


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(@wvreeven)
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(@mkeller0815)
White Dwarf Customer
Joined: 2 years ago
Posts: 22
Topic starter  

@wvreeven what do you mean by "normal" frames? 

I just checked the other thread but it is about the native or / and  ASCOM drivers together with APT changing the Bayer pattern during a session. But it seems that in both of my session the pattern is consistent. I'm also using the INDI lib and KSTAR for imaging what is a completely different software stack. I reached out to @daniel_n because I know he also uses the ASI183MC pro and APP but with different imaging software and he confirmed that his images also appear blueish. 
I also tested my session in Siril and had the same output there. So probably it is the way this camera records data even though I don't understand why this happens. 
It looks like the the blue part of the pixels get a higher offset because just the dark parts are more blue. looking at the stars in high magnification there are gray tones not blue tones. so the more signal we have for a pixel the less the effect of the  "blue shift" is. 

 What I can try is to add a normal lens to the camera (if I have the right adapter set) and take a daytime picture of objects with well know colors and maybe even a grayscale test page to see if this also adds this blue tone to everything.

This post was modified 1 year ago by Mario Keller

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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1723
 

@mkeller0815 With normal I mean the ones that look green. But now that I read your original post again, it looks like ALL your images are blue! Sorry, I misunderstood that.

This is strange. Did you ask in the astroberry sub-forum of the INDI forum if anyone else experiences the same? This seems to be either camera or imaging software related. Perhaps we can help you configure APP such that it can produce natural colors from the images you took but I'd want to know the cause of the issue as well.


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(@mkeller0815)
White Dwarf Customer
Joined: 2 years ago
Posts: 22
Topic starter  

Yes, all images are blue. After testing with Siril I also think it is not APP related and running the "neutralize background" the image looks natural. So I can overcome this issue, but still it is strange. There is a thread in the indi.org forum 
https://indilib.org/forum/ccds-dslrs/3922-right-settings-for-asi-183-mc-pro-in-indi.html#gallery-1
and the last post also states that the images have a blue tint. If we would have the data of all 4 subpixels (before debayer) of one image pixel with a color that has different values for R G and B we should see that two subpixels should have more or less the same value and this should be the green subpixels, right? Maybe I find the time next week to play a little with the astro.py library in python to get something we can look at. 


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