Re: New AP scope and more

From: Thomas Womack (twomack_at_chiark.greenend.org.uk)
Date: 11/01/04 

Date: 01 Nov 2004 19:31:21 +0000 (GMT)

In article <20041030152820.18077.00006118@mb-m03.aol.com>,
Chris1011 <chris1011@aol.com> wrote:
>> NASA or the large observatories use ion milling and other computer
>>controlled methods rather than hiring Mr. >Zambuto or Swayze .
>
>None of that is necessary for lenses. Today there are computer controlled
>grinding and polishing machines available that eliminate the need for much
>direct labor. Most of us use these machines to produce high quality refractor
>optics.

> Costs will not go down much in volume because of the high cost of
> energy, which is needed to produce glass, especially so for ED and
> Fluorite materials, which need 3 to 10 times as much energy to
> produce vs. standard crown and flint glasses.

Given that you don't have to change the temperature quickly (indeed,
you have to be fastidiously careful that the temperature changes
almost not at all in the annealing), isn't this almost an insulation
rather than an energy-input question? The original melting is
unavoidably costly, but it sounds as if the expensive part is keeping
the furnace at temperature for weeks at a time.

I suppose fitting a glass-annealing furnace inside a Dewer flask would
be a little impractical.

Tom

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