I havent had any problems with dewing up for a long time, then Saturday night whilst imaging the Moon with my Meade imager and Autostar software, halfway through the session, the little box that shows "image quality" started showing 0%. I thought this crazy, so went outside and gazed up at the Moon. There she was shining nice and bright. Went inside and still 0%. Took me a while to suss out that it was indeed the front lens completely fogged up!
It is the dry season here for goodness sake - so yes, Brissie does get dew>
Guess what I made yesterday - a dew shield from an old foam rubber sleeping bag and some contact glue. looks odd but I am hopeful it will work - otherwise its the wife's hairdryer.