Re: [ATM] Scopes for the masses

["Bob May" <rmay@nethere.com>]

I'd only consider that glass to be good for making a Schupmann
telescope.  You can get a3ay with two disks as they probablly
will be very similar in refractive properties that you will be
able to tune out most, if not all, of the color error.
A disk 20mm thick and 13 inches diameter (forgive the mixed
measurements but 13 inches isn't in my lexicon of metrics) was
$300 for a guy in the grinding group.  That was also including
pregenerating of the curves on the glass and it was BK7.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net

----- Original Message -----
From: Dominic-Luc Webb <dlwebb@canit.se>
To: ATM Superheros <atm@atmlist.net>
Sent: Friday, May 02, 2008 12:39 AM
Subject: Re: [ATM] Scopes for the masses


>
> On Thu, 1 May 2008, David Harbour wrote:
>
> > With a +.25 or +.50 diopter unprocessed opthalmic blank (a
glass one) from
> > your vending optician, and some Sparco "telescoping" mailing
tubing (I kept
> > my small hoard of this tubing) it is easy to build a very
serviceable 2"
> > refractor; then, get a cheapie eyepiece for it-
> >
> > R-101
>
> While we're talkin cheap...
>
> You maybe noticed that a couple threads ago I mentioned
> a source of very thick plate glass was theatre lights?
> I would have to measure exactly, but as mentioned
> earlier, the focusing lenses I obtained are around 150
> mm diameter and maybe 70 mm thick. Normally we would
> just buy proper optical glass, but since these were
> free, and more can be had cheap or free, I decided to
> hang on to the two that I have and give this a try
> sometime. I would imagine optical glass of this size
> would be quite expensive and can't imagine optician
> blanks this large.
>
> I therefore wonder if anyone has tried using thick
> plate glass for a refractor objective?
>
> Dominic-Luc Webb
>
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>

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