I have used since I can remember for all my photography and astronomy accessories the cheap black velvet adhesive sheet that they sell for young people to line their books.
If it is used only with its adhesive, the sheet peels off after a short time. I paint with contact glue (I do not know if this term is understandable in English) the surface where I'm going to put the velvet, I let it dry and then I stick the velvet sheet. It is eternal. If, instead of using "industrial" contact glue, a graphic designer contact glue is used, it can be easily peeled off with a drop of zippo gasoline for lighters.
3M has Photo Mount spray in both versions, Permanent and Removable, but I I prefer the application with a brush.
Time ago I published in this forum that for quick solutions in small diameter tubes I use with success rough rubber sheet of those used to waterproof roofs. I suppose that the engraving helps to eliminate reflections, but it works very well, I always have pieces around my microscope, and I do not need to fix it, its elasticity holds it to the tube.
That's what I have and it works well, so does the Protostar if you want a sticky back. I use the Beetle Black like Robert indicated, just roll it up and slide in, sometimes may use some double sided tape too.
Just be sure to roll it with a lint roller to collect most of the loose fibers.
Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike
