ATM eliminating dew in unheated observatory

[Bob Rubendunst <softm@softm.com>]

The Champaign Urbana Astronomical Society has a 16 inch classical Cassegrain telescope in 
unheated dome. As the weather changes, the mirror dews up, and after five years, the 
mirror is in bad shape.

The dome is rural, and the only source of power is a modest solar panel.

Currently we throw a plastic cover over the 'scope when we close up the dome. Some have 
suggested using cloth instead. Some have suggested a fan to circulate air in the scope. 
Some suggest heating the mirror, but I doubt we have the electrical capacity to keep the 
mirror heated 24/7.

What works best, given that we have very limited electrical power provided by a 25W solar 
array and a 12V battery?

Bob Rubendunst