ATM Newby Questions

[Adrian Wallace <adrian@ratherbeflying.net>]

I've just cleaned my 10" (s/h) mirror, and the surface is nothing like
the bit that was protected by a mounting tab. The protected part looks
new. It looks like smoked glass or has a sort of tarnished/dusty 
looking surface. It will need a lot of pressure to clean it. Is it
possible to remove this? 
There are flaws in the surface etc and the mirror probably need
re-surfacing soon anyway.
I took pics of the mirror before cleaning it, but I'm too ashamed to put
them up now!

Also, is there a way to check the focal length of the mirror in situ?

Thanks, Adrian.

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