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Re: [ATM] Thick plate glass for objective lens
I'm thinking of doing that with the plate glass tool I have leftover from my
12.5 inch. Worse comes to worse, I'd have a really neat magnifying glass.
I did that with a 6" years ago. I mounted it on a 2x4 and made images of
the Sun at least.
On Fri, May 2, 2008 at 9:21 PM, Richard F.L.R. Snashall <rflrs@rcn.com>
wrote:
> David Harbour wrote:
> > Dominic Luc-Webb wrote:
> >
> >> I therefore wonder if anyone has tried using thick
> >> plate glass for a refractor objective?
> >
> >
> > This HAD to be the case for the very long single element objective
> > refractors of the 17th century; I remember an article in Sky and
> Telescope
> > that featured Richard Berry's "re-creation" of a smaller version of one
> of
> > these immensely long focal length refractors; if I remember correctly,
> he
> > used a grade of greenish plate for the lens, and gave it an enormous
> focal
> > length, and then, stopped it down; it gave a creditable performance;
> there
> > was in his article, a snapshot of the moon taken through it. No
> apochromatic
> > whizz bang, but proof that one can accomplish a functioning telescope
> with
> > plate glass for an objective, albeit, a very, very, very long focal
> length
> > one. Did any of those guys in the 1600's- Cassini, or the other guys who
> > built those ultra long tubeless "aerial telescopes" have any other kind
> of
> > glass? I don't think so. I may be wrong, though.
>
> Remember those camera obscura we worked out? I've hacked at
> it a bit more. Maybe a quasi-symmetric version could work
> better:
>
> Title: camobs1-12x
>
> 200 mm Camera Obscura for 3 m focal distance
>
> Surf Radius Thickness Glass Diameter
>
> 1 789.1 11.9 OPTIWHITE 240
> 2 1097.2 84.2 240
> STO Infinity 103 196.12
> 4 -1454.6 13.5 OPTIWHITE 240
> 5 -1007.9 2795.644 240
> IMA -1568.257 990.2
>
>
>
>
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