alacant wrote: ↑Fri Oct 13, 2023 9:11 am
I've noticed that too. Have you found a workaround or set of values (maybe in shrink?) to offset the ringing?
This is an example. Yes, it's enlarged beyond normal but it shows the effect I think you're describing; small stars against nebulosity.
We find that it can be fixed by increasing the colour radius in Shrink. The problem is getting all the small stars in the mask. Stars which are included in the mask for Shrink merge well with the background. The smaller stars which are not masked remain with the dark ring around them. Playing around with sensitivity, even on the most sensitive setting, the smaller stars will not be detected.
Yeah that's pretty much the post-SVD culprit there. One of them anyway. I do use Shrink to touch this up when I am ready for a final version, usually at the very end. For interim images and sometimes even finals, I'll just leave things be. Depends how obnoxious it looks, and occasionally those little dark rings sort of kind of help little stars pop out. Not that it's proper, but sometimes doesn't look bad.
What I do though is just a fully manual mask, no actual shrinking iterations, just deringing pixels usually 1.5 to 2.0, and I zero out the color tame as I don't want to alter any of that up.
It's a fair bit of elbow grease to accomplish, as one has to be zoomed in and then just pan across and down the image hunting for all the little rings. Also, these stars are so tiny that the mask controls aren't quite up to the task. I find using the drag-circle option quickest, though that's still awkward. What would be best would be a variable sized circle and you'd just apply it with a click. Like toggle single pixel, but that's too small.
I have had difficulty getting all these tiny stars included in a mask using the various automask settings. It still often misses them, or worse ends up including non-stellar features. Really I don't even want all tiny stars masked, just the leftover ringing ones. Reason being that the deringing actually imparts a bit of a fade/blur around the target mask. Perfect for remedying the ringing, but I don't want to fade and blur other features or the tiny stars that don't need it. Thus, fully custom mask.
It's really not too big of a deal, just a little task to do. Though some heavily nebulous images can be more work.