I recently finished building my observatory and mounted my new DDM60Pro on the pier for the first time. As soon as I was ready to start initial polar allignment a long period of cold wet weather happened. We had 250mm of rain and I was very pleased that there was no sign of any leaks in the observatory (a Sirius 2.3m). Then the sun returned but temperatures remained low. It was at this point that I entered the observatory during the day and was alarmed to find the entire pier and mount wet with condensation. I realised that with the sun warming the observatory walls that the mount and pier were now the coldest part in the building and thus were collecting the atmospheric humidity as condensation.
I decided that if I was able to raise the temperature of the mount slightly that this may solve the problem.
So I have made a small heater to sit inside the mount on the baseplate. I soldered three 68 Ohm 9 Watt wire wound resistors in parrallel and placed them in the bottom of a diecast metal project box and half filled the box with epoxy resin. I attached an old scanner power supply (measured at 14.3 volts). So with around 23 Ohms and 14.3 V we get just under 9 Watts. I then added an LED to indicate that the heater was running as it is not possible to feel any warmth when the heater is in position as the mount conducts the heat away so well.
I am now running this heater continuously and, so far, it seems to be working. By touch, the mount is just slightly warmer than the pier and although some condensation still collects on the pier, so far the mount has remained dry.