Re: ATM Nothing but heat....

[schmidt@coyote.csusm.edu (Michael Schmidt)]

>                      Subject:                              Time:  5:32 PM
>  OFFICE MEMO         Nothing but heat....                  Date:  9/19/96
>
>From: K1JJ@aol.com
>Date: Tue, 17 Sep 1996 16:03:24 -0400
>Subject: Re: ATM How much heat?
>
>In a message dated 96-09-17 14:22:29 EDT, you write:
>
>>A fan helps, but if dew has already formed, nothing but heat will burn it
>off.
>
>I was wondering if you could use a fan to force air over a desiccant, and then
>flow this into the tube assembly (with appropriate filtration to prevent the
>desiccant from getting onto the mirror). The air could be at ambient, but
>should have
>a lower dewpoint. It might not suck moisture off an already dewed mirror, but
>perhaps it could inhibit dewing. Nothing but heat?  Anyone willing to test?
>                        ....RICH

I would guess that the dessicant would be saturated fairly quickly, and
then you have the mess of "regenerating" the dessicant by heating. If you
really want to dry the air in a more continuous fashion, maybe you need a
peltier or refrigeration unit to create a cold screen to precondense the
water vapor on the intake. I don't know what effect this would have on the
air temperature going into the telescope--it could be cooled by the cold
screen, but the latent heat of condensation might offset this somewhat.
Seems like heating might be the best idea after all. . . .