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xoxoxoBruce · 11-08-2003, 07:53 PM

Actually, unlike lenses the mirrors can be made of a number of different materials. The last telescope I put together had two mirrors (24" & 12") of ground Beryllium. The big bugaboo is the coefficient of thermal expansion causes most materials to distort the image with temperture changes. Of course all materials move some with temperture changes even concrete.

11-08-2003, 07:53 PM	#4
xoxoxoBruce The future is unwritten Join Date: Oct 2002 Posts: 71,105	Actually, unlike lenses the mirrors can be made of a number of different materials. The last telescope I put together had two mirrors (24" & 12") of ground Beryllium. The big bugaboo is the coefficient of thermal expansion causes most materials to distort the image with temperture changes. Of course all materials move some with temperture changes even concrete. __________________ The descent of man ~ Nixon, Friedman, Reagan, Trump.