Phil
I've got the same problem with my flip-top obs.
http://www.iceinspace.com.au/forum/s...ad.php?t=81602
I'm thinking a 50w solar panel, regulator, 12v 7AH sealed battery, 2w resistor, 12v fan, 12v relay and a motorcycle cover.
When the sun comes up the 12v relay kicks in and the low mounted fan blows out the dense moisture laden air and the panel charges the battery. When the sun goes down the 12v relay kicks out and a 2w resistor turns on and runs all night under the cover keeping the gear warmer than ambient (maybe!). Might be overkill but I'm going to give it shot. Bought the bits and will let you know how it goes in a month or two.
Cheers
Stephen