(meteorobs) OT -Technical question on Hemispherical MirrorUndercoating.

[Chris Peterson]

The mirrors we used to use were backside aluminized, and then protected with 
some sort of paint. That's pretty typical for most mirrors. When 
experimenting with antidewing methods, one thing we tried was incandescent 
light bulbs. As you note, pinholes allowed light to leak through. So we just 
painted the underside of the mirrors with flat black paint directly, no 
varnish in between. That worked just fine. A couple of mirror based cameras 
still in operation have shown no ill effects, even after several years of 
operation.

BTW, we abandoned light bulbs in favor of heat pads, since the latter are 
thermostatically controlled and turn themselves off in warm weather.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "stange" <stange34 at sbcglobal.net>
To: <meteorobs at meteorobs.org>
Sent: Tuesday, December 16, 2008 9:05 AM
Subject: (meteorobs) OT -Technical question on Hemispherical 
MirrorUndercoating.


>I have a concern with heat transfer & any acidic action of SPAR Varnish
> followed by a coat of Krylon Ultra-Flat Black paint on the 
> underside(inside)
> surface of a hemispherical mirror which does not appear to be metallic.
>
> Objective is to remove trace light leaks which will be evident with a very
> sensitive low light camera and still allow good (internal) heat transfer 
> to
> mirror dome surface to counter dewing.
>
> Anyone with experience in adverse effects of having done this?
>
> Physical science & Chemistry input appreciated for the IR blocking system 
> we
> have developed.
>
> Thankyou.
> YCSentinel