Re: ATM weather and mirrors

[Brian Nestel <blast@aloha.net>]

Darwin Teague wrote:
> I am about to get my 10" scope going - the mirror is being coated.
> I have an observatory and am wondering if I would ruin the coating if I
> left my scope out there all of the time.
> The observatory has open spaces around the bottom (the walls don't touch
> the ground and there's no floor in it). There is also open space between
> the rafters on the roof.
> I know rain won't get in, but I worry about moisture condensing on the mirror.
> Under what conditions would moisture build up on the mirror? Only during fog? 
> If I had both ends of the tube covered and the eyepiece holder plugged,
> would this reduce or eliminate the problem?
> Would there be a problem in winter? I'd hate to take the mirror in and out
> then, because of temperature differences.....
> I'm using one of Richard Berry's designs (10" dob), so the mirror actually
> keeps it's alignment pretty well when I take it out and put it back in
> later....
Hi:
Depends on the average humidity in your area and temperature range. When
I
lived on the east coast I had little moisture problem during the winter 
because the air is dry, most of the problem was during the summer when
it
rained and the humidity was up. I usually stored the scope on the mount
at
a 45deg angle with the ends covered and with the eyepiece holder down 
so no mirror surface was perpendicular to vertical, it keeps dew from
settling on the surfaces, during times of high humidity I would also
put a bag of dessicant in the OTA, storing in this position also keeps
dust from settling on the surfaces. 
The climate here is alot different the humidity is high over 50% most
of the time so I keep the Newt OTA in the house when not used with a
bag of dessicant in the tube and the ends covered. I have hinged split
rings on the mount to make removing the OTA easy.
-- 
Aloha   159 36 W, 21 58 45 N
Brian   Middle of the Pacific,
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