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Mirror material

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  • Rocky
    I know that BK7 is better than soda-lime plate glass but is it a major difference. I have a chance to get a 8 Newt F4.9 and if there is not a major difference
    Message 1 of 2 , Nov 1, 2010
      I know that BK7 is better than soda-lime plate glass but is it a major difference. I have a chance to get a 8" Newt F4.9 and if there is not a major difference then I will get it.

      With all the mirror making the club has done there must be one of you who can answer this question.

      Thanks Rocky
    • Don Surles
      Rocky, BK-7 is typically used for lenses, and some prisms in less expensive binos are made from BK-7. You will probably never see any difference in the
      Message 2 of 2 , Nov 1, 2010
        Rocky, BK-7 is typically used for lenses, and some prisms in less expensive binos are made from BK-7.

        You will probably never see any difference in the performance of a mirror made from BK-7 or soda lime.

        The material of choice is Pyrex for it's low coefficient of expansion...but once the mirror has reached ambient temperature the coe should not be significant.

        I would be concerned with the thickness of the mirror...it should be more than 3/4"; I would also be concerned with who made the mirror (Chinese, amateur, or American company) and the figure.

        don...


        Nov 1, 2010 02:15:37 PM, delmarvastargazers@yahoogroups.com wrote:

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        I know that BK7 is better than soda-lime plate glass but is it a major difference. I have a chance to get a 8" Newt F4.9 and if there is not a major difference then I will get it.



        With all the mirror making the club has done there must be one of you who can answer this question.



        Thanks Rocky
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