Optional standard remote sensors are available (2RSCDDDH-D) to operate differential mode dew removal. One sensor is needed to operate Channels 1 and 2 output and a second sensor is required to operate Channels 3 and 4. These Remote Sensors allows you to control the heating of separate optical elements. For instance, one remote sensor would be placed with your heater at the corrector and a second sensor could be placed on your finder scope objective lens or eyepiece or use two sensors on one large objective with two heater straps control. In these setups, each pair of heaters are controlled by their respective sensor while the supplied ambient temp sensor which comes with standard CDA-R or RC-CDA-R purchase can be placed on the main optical tube objective for ambient sensor collection. Using these sensors in this configuration allows greater dew control for the user.