RE: ATM How to make a heat coil to reduce dew?

["Bertapelle, Ken" <Bertapelle.Ken@tci.com>]

Hello Olle,

I believe Dave Kriege sells something like this for preventing dew build up
on secondary mirrors.  I think it's called "hot wire", or "heat rope", or
something similar.  Check out the Obsession Telescope site.  There are
probably lots of other places you can get it as well.

- KenB

> -----Original Message-----
> From: Olle Eriksson [mailto:olle.eriksson@telia.com]
> Sent: Tuesday, June 29, 1999 12:00 PM
> To: ATM
> Subject: ATM How to make a heat coil to reduce dew?
> 
> 
> 
> Hello everybody
> 
> I am in the middle of building a portable 8" f6 Dobsonian. I 
> came across a
> fan from an old computer today and I though about using it behind the
> primary mirror to reduce its cooling time. When I started looking for
> battery cells on 12 Volts it occured to me that I might use 
> the available
> current to also power a heat coil of some kind to reduce dew 
> formation on
> the mirror. If I am not completely wrong, dew will more 
> easily form on a
> mirror when the telescope has an open tube.
> 
> Does anyone know how such a heat coil could be made and what it would
> consist of? Any ideas, photos, or anything else is very much 
> appreciated.
> 
> I know the fan uses 0.16 A. How many Ah would you recommend a 
> battery cell
> to have for the fan and the heating device?
> 
> I might also want to use the power cource to run an 
> equatorial camera mount
> sometimes. This thing consists of 12 V stepper motor (48 
> steps/r) and a SAA
> 1027 stepper motor control IC. The problem is I don't know 
> how much current
> it draws.
> 
> Sincerely
> Olle Eriksson
> http://www.astro.homepad.com
> 
> 
>