Ah interesting…I’d seen that effect on a couple of my images but doesn’t really bother me. Good to know what causes it though
Looks like it should be easy enough to make one out of black foam or plastic, and a circular cutter as bojan suggested.
The CN thread also talked about affixing the mirror to the clips with silicone…I’m not convinced that would be without its issues though. With my f/4 newt any mirror slop in the primary cell wrecks collimation.