Last weekend, after over 3 months of lousy weather, the clouds blew away, and out came my beaut 12 inch Lightbridge. When I undid the mirror cover, I saw a large black mark near the outer edge
Out came the rubbing alcohol, but it made no difference. The mark was completely black and 6 mm in diameter. Around this black mark was a 2 mm wide whitish blemish - all told 10 mm diameter - OUCH
The mark seems to be under the surface - not on it. Would this be the silvering deteriorating? How do they put on the silvering? I would have thought it would go on top of the glass
Anybody got any ideas? Is it likely to grow? Remember, this mark is not on the edge of the mirror - about 15 mm in from the edge.