Re: [ATM] Cutting glass into large circles

[David Weinshenker <daze39@earthlink.net>]

Bob May wrote:
> My 200" refractor has shown me the light of long focal
> length telescopes for planetary viewing.

How did you build a 200" refractor? (What was the aperture?)
Did it have a conventional tube, or was it more like Huygens's
old "aerial" telescope from the 1600's?

I hear you on the long focal length bit - Jupiter through the
40 inch f/15 Cassegrain telescope at Lick Observatory was
something to see...

I've been thinking of a design similar to a Cassegrain, but
with the convex mirror replaced by a negative lens and a flat
mirror behind it - sort of like a two-pass "Barlow" lens. This
looks like it will give a long, adjustable (by way of changing
the spacing between the concave lens and the mirror) focal length.

-dave w
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