Re: [ATM] asymptote to ambient

["Jan van Gastel" <jhm.vangastel@wanadoo.nl>]

Fans are also very helpfull in warming the mirror up after the night has
ended, when the ambient temperature rises faster then the mirror temerature
and they then prevent the mirror from being wet for hours.

Jan
http://home.wanadoo.nl/jhm.vangastel/Astronomy/

----- Original Message ----- 
From: "Mark Holm" <mdholm@telerama.com>
To: <atm@atmlist.net>
Sent: Wednesday, February 09, 2005 12:01 AM
Subject: RE: [ATM] asymptote to ambient


> Donald Good wrote:
>
>
> >I read in a recent review of dew heaters that a mirror can drop below
> >ambient by radiative cooling.
> >
> Yes, and with today's much more open designs, the mirror is more open to
> the sky, thus will cool more by radiative cooling.
>
> This is also another argument for fans.  When radiative cooling is
> significant, a fan will actually help keep the mirror warmer.  If you
> happen to be in a locale where air temperature does not often drop below
> dew point, but a radiatively cooled surface might, then a fan might be
> all the extra edge you need to keep away dew.
>
> -- 
> Mark Holm
> mdholm@telerama.com
>
>
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