Hi John, I would recommend dew heaters over the hair dryer.
You can buy them, but they are expensive. Homemade heaters are just as good and A LOT CHEAPER. If you are handy with DIY there are articles in the projects section of I.I.S. on how to make them.
I have made them for my scope and couldn't live without them, and I don't have to think about it once turned on.
John.