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Just a final comment on this equilibrium concern, this has been debated across the internet for years, and in astronomy glass material opinions are like navels - everybody has one. There is little difference between BK7 and Pyrex in practice, however, BK7 is generally acknowledged as being as better optical glass (more homogenious, which may not matter much when used as a mirror but does as a lense). All you have to do is google BK7 vs Pyrex and there is heaps to read on the subject, including an interesting IIS thread where Mark raised the that claim originally. There is also plenty written about GSO mirrors.
BTW the 16" mirror is 45.3mm thick.
Suffice to say, that given the 16" GSOs great fan there is little to be concerned about. If you want the ultimate in equililibrium tooling do the GSO fan mod covered in the the Projects & Articles section, and install a tube baffle to direct air over the surface of the mirror and shroud the rear.
Last edited by glend; 11-03-2014 at 09:40 PM.
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