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Posted by Robert May on August 9, 2002 18:59:54 UTC

I'd go with the 19mm glass for a first pass. There are things that you will learn with this first try at grinding that will cause problems with a thinner glass, including overshooting the desired curvature.
As to focal ratio, the problem here is that the shorter FRatios tend to be a lot more difficult to figure as they are more of the parabola and the Foucault test becomes harder to do well.

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