Instruction manual

25
• The internal temperature of the controller is increased if the duty cycle is set above zero or if the
controller is placed with the sensor toward the top (power switch end up). Zero to full duty can raise
the sensor as much as 25F. This will introduce a measured temperature offset; however, so long as it is
stable or at least tracks the scope, there will be no error introduced in the temperature compensation.
In general if using the internal sensor, we recommend a duty of zero, or at most 10%. If using the
internal sensor, you should NOT change the duty while an imaging run is being made as the duty
change may change the temperature and introduce a focus shift.
• The time constant of the RoboFocus controller may be different from the scope. In fact, the scope will
likely have several different parts (tube, mirror, etc) that contribute to temperature focus shift, and each
component will likely have different time constants. Even more complex, the rate of change with time
of temperature in the observatory and the presence of airflow will affect the overall ability of a sensor
(even an external sensor on the scope tube) to track the effective temperature.
In most cases, simple steps such as reducing the duty cycle or installing a small fan in the observatory will
eliminate operational problems arising from thermal tracking issues.