Autostreaching an OSC image

I’m using a OSC camera (ASI534MC) and I’m used to see “green” images from the camera or in the first steps of my processing workflow. Usually I choose AutoStrech visualization to help into identify gradients / defects. But this option is of reduced before the color balance. Usually what I get is:


But today, I was trying ASIStudio and I’ve seen that the same FITS on their FITS viewer looks like:

As you can see no green tint and a more useful visualization. Also in Pixinsight the autostrech remove the green dominant.

Investigating about what is doing SiriL I’ve tried to split the original image on R,G and B components, autostrech each component (with the histogram tool) and composed again a RGB image:


Now this is the kind of autostrech preview that will be very useful. For example, I can see quickly that I have a gradient to remove and some green tint that the SCNR can fix quickly


So, the question is, why the current preview scheme is applied? Could be for performance reasons?

This is because, and this is my choice I assume, we apply autostretch with RGB linked. While some software unchained the channels.
Why I choose to link the channel? Because User is aware he needs to apply the color calibration tool. Doing autostretch on unchained channels changes (only for visualisation) the white balance. This can mislead the user.

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Histogram stretch performs a stretch (stronger) with unchained channels.

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Yes I know that Histogram option has unlinked channels but it is so extreme that’s I feel it lees useful that auto stretch (once I’ve balanced the color obviously). Ok, thanks for the information

Once stacked. You need to check for gradient removal. For that, Histogram stretch is the best tool.
Then, right after you need to to calibrate your color. So you will see the change in the autostretch mode in live.
Then, after you will have the right colors very soon in the process. This is why I think this is not a big deal.


My “use case” right now is that I’m applying background removal, before color balance (I’m removing light pollution, so it will be the first operation performed). To evaluating the removal I’m forced to use Histogram that is too strong. So at the end I’m blind removal the background, color balancing, auto stretch and then if the first step is not right, undo, undo and repeat.

Ok, I’ll try to follow your advices

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I always use histogram tool for gradient removal. That helps me a lot to see very faint gradient !
If you manage to have an almost flat image in “Histrogram” mode, then you will be really happy with your image at the end.

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