[ATM] ATM: Opthalmic blank magic-

["David Harbour" <scarab2@cox.net>]

Hey, guys-

I am 100% certain that I saw an article in Sky and Scope, one solar eclipse
year (not too long ago; perhaps a decade or so) where a fellow explained
that one could calculate how to obtain an ENORMOUS effective focal length,
by applying a certain formula, to calculate which two opthalmic blanks, each
of a given diopter, would do when taped together, spaced considerably, back
to back. Do any of you guys remember this? It seemed enormously clever to
me; he was able to project an image of the eclipse an enormous number of
feet away. He gave the formula for picking the apppropriate blanks, and
providing their spacing. Does no one remember this?

Davey


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