David,
thanks for those tips. The mirror is well less than two years old (it's on a Meade 12" LB), but as for the pin-holing, I'm afraid I didn't check that while the mirror was out. I knew I should have left it until I'd got a few replies to this question - drat
However, I did get the impression whilst washing and holding etc, that the blotches were surface imperfections rather than holes in the coating.
I may take it out again to check in the next few days to check this. I'll wait to see what other pointers get posted
Thanks again David
