Living near the wettest place in England, dewing is ever present hazard for me but with this specific ATIK camera model which I have been running for many years the only time I have had a dewing problem has been when water got into an SCT when it got rained on making the air inside the telescope particularly humid. The dew then was on the outside of the camera window and drying out the telescope solved the problem. If this is a reoccurring problem (eg with an open tube telescope) this is where a specific dew heater for the camera could help. The other possibility though is dewing internal to the camera, either on the inside of the camera window or on the sensor cover glass (this can actually be frost if the sensor is cooled,as here). In the ATIK cameras, this is prevented by making the chamber in front of the sensor hermetically sealed and the air kept dry by a desiccant tablet. If the dewing is on the inside it is because the air in the chamber has become wet (either over time or because the seal has failed) In this case opening the chamber in a warm dry environment, introducing dry air and recharging the desiccant as ATIK recommend will solve the problem, though the solution may be temporary if the chamber is leaky.
Cheers
Robin