Limitations are imposed on conditions when the telescope may be safely operated. If you are open and any of these limits are exceeded, the enclosure must immediately be closed. The enclosure will remain closed until the Observatory Support Assistant on duty determines that the conditions are within safe operational limits.
These numbers were put into effect for prime-focus observations and will be reviewed and revised as needed. In particular, installation of the adaptive secondaries are likely to require more stringent limits.
Temperature
The lower limit to the operating exterior temperature is -20°C. There is also a differential temperature limit of 10°C with respect to the mirrors to minimize thermal stress on the glass. Note that differential temperatures can often exceed this when closed for several consecutive days due to winter weather and the enclosure and telescope will need to be carefully cooled prior to opening the enclosure for observations.
Wind Speed
The telescope can operate in sustained wind speeds up to 40 miles/hour (17.9 meters/sec) or gusts up to 40 miles/hour (17.9 meters/sec).
Humidity and Dew Points
The upper limit to the relative humidity at which the telescope can operate is 95%. There is an additional requirement that the dew point temperature must be safely (>2°C) below the temperature of any part of the telescope, especially the mirrors.
Snow Accumulation on the Enclosure
The roof of the enclosure must be free of any snow or ice that can blow into the enclosure and onto the telescope.