Starless Images and Stretching - Part 2

I just watched this video, where you explain this technique, which is actually the one I've been using. In the end, you notice the dark ringing around stars in the image which had separated stretches - I believe these are not coming from small stretch as you mention but from the fact that the stretch applied to the stars had the black level raised a bit. By my experience, that is the main factor driving that ringing and I believe it must be kept at 0 when stretching the stars.

Cheers,

André