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Foucault Tester With Bad Eye Relief!

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Posted by mayen1@mwt.net on June 11, 2000 15:53:04 UTC

Hello all,

I`ve ran into a problem many years ago with the long focus solar
scope I made. The 4.25" f-15 mirror was so small, because it was so far
away it was hard to see the incredible subtle shadowings that were going
on there. I remember using a modified finder to get a "Closer" view.

Now I have the opposite problem here. And I`m wondering if there is
a simple way around it. I`m going to be shortly working on an old
project that I hopefully have found a design for, but testing the mirror
is very hard to do. It is that 15" f-1.1,, the light cone is so fat that
when using a foucault tester or even ronchi rulings to be able to see
the whole mirror fully illuminated your eye nearly has to touch the KE
or rulings. It`s like almost putting on contacts! Your eye begins to
water cuz it knows there is something so close it is about to poke it he
he he.

So is there anyway to get i guess you could call it "Better Eye
Relief"?

Joe

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