Hi,
Would you be able to send us some more information about your camera? (e.g. manufacturer, model, etc.)
If possible, you should avoid JPEGs and in-camera stacking at all times. The JPEG format is only 8-bit, does not allow for faint detail, has already been stretched, has lossy compression applied and - usually - has all sorts of other operations applied that make detail recovery, color calibration, light pollution removal, etc. impossible.
If you have absolutely no other choice, you can choose "Attempt to reverse stretch". This will undo the sRGB stretch that JPEG encoding applies, making the data linear again (in theory). This will allow you to engage Tracking mode and use all the modules that only make "mathematical sense" when used on linear data.
All that said, you can use the Magic module to shrink you stars, even with post-processed JPEGs.
You first need to make a mask, that contains the stars that you want to shrink. If you have "fat" stars with overexposed cores, those are usually the stars you'll want to target.
Mas > Auto, set 'Selection Mode' to 'Highlights > Threshold', then choose a brightness 'Threshold' above which you want to select pixels. For example 85%.
Click 'Do', and you will now have a mask overexposed star cores. You will want to 'Grow' the mask a little (click 'Grow' a few times), to include more of the stars.
Now 'Keep' your mask. You should now be ready to use it in the Magic module (use 'Iterations' to shrink more);
For example, you can go from this;
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- 1.jpg (156.86 KiB) Viewed 8025 times
To this;
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- 2.jpg (140.45 KiB) Viewed 8025 times
Do let us know your camera's specs. Hope this helps in the meantime!
