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Subject: RE: [M]:Dew and heaters
From: Bill Arnett
Reply To: mapug@shore.net
Date: Sun Dec 14 01:07:24 1997

At 10:12 PM -0800 12/13/97, Michael Hart wrote:
>... I have used
>an infra-red thermometer repeatable to 1% of reading

Is that one of the ones that doctors stick in your ear? Could you use it
to measure the temperature at various points on the corrector? (One of the
things I worry about is the temperature differential across the corrector
when it is heated only from the edge.)

> and found a delta-T
>of less than 2 degrees easier to maintain than you might think, a simple
>rheostat is adequate, and THAT is overkill. There is quite a bit of radiating
>surface on a metal telescope exposed to the night air in proportion to the
>heat added...

In an attempt to make my dew heater more efficient, I put the resisters
right on the ring that holds the corrector in place. I'm thinking of
replacing this with nichrome wire underneath that ring directly in contact
with the corrector's glass. Is that a bad idea? My reasoning is that it
is a waste of energy to heat all the metal. But am I making the
temperature regulation problem much worse?

---
Bill Arnett "Science is a way of trying
San Jose, CA USA not to fool yourself." -- Feynman
billa@zNet.com <URL:http://www.seds.org/billa/>