A dew sensor is mounted at the top of the Nickel secondary mirror housing. The dew sensor control box and readout is in the Nickel control room. The data are also available on-line from local computers on the rapid weather update table and the dew sensor readout which updates every few seconds. When dew is detected on the sensor an alarm will sound from the dew sensor control box. If the alarm sounds, the mirror cover and dome must be closed immediately and the ventilation fans turned off. Ideally, the observer will keep an eye on the humidity and close the dome before dew starts forming on the telescope, thus preventing the dew alarm from sounding.
It may take some time for the dew to evaporate from the sensor once it is triggered. Thus it is possible to temporarily silence the alarm (please only silence the alarm when the dome is closed!) by pressing the Silence/Next button on the controller.
Please do not push the Up and Down buttons as these change the default settings for the sensor. Any changes may put the telescope at risk for water damage.
Observers are expected to monitor the weather while observing using the tools and information listed on the Mount Hamilton Weather page.