UNIVERSITY OF CALIFORNIA OBSERVATORIES / LICK OBSERVATORY

3-M WEATHER LIMITS HOME
3-meter observers should be aware of the following conditions which limit or prevent operation of the telescope.

Note that these limits are only guidelines.
The decision to open or close the dome is entirely at the discretion of the telescope operator.
Wind Limits

Average (MPH) Persistent Gusts (MPH)
Into Wind3540
Crosswind4045
Downwind4555

Exercise caution using windscreen as windspeeds approach limits.

Humidity
94% or at the telescope operator's discretion based on blowing fog, condensation on dome and handrails, etc.
Ash
Telescope Operator must close if airborne ash from a forest fire is deemed a threat to the optics.
Snow on Dome
If snow has accumulated on the dome and not been shoveled, the telescope operator will keep the dome closed to prevent snow from falling or blowing onto the telescope.
Lightning
If distant lightning can be seen but no thunder heard, there is no immediate threat and observing may continue provided there is no danger of rain.

If lightning is 10 miles away or less (about 50 seconds from lightning to thunderclap), there may be danger of a strike. Telescope operator can stop observations to shutdown critical electrical systems at his or her discretion.

Wait at least 30 minutes after the last audible thunderclap before declaring the storm passed and resuming operations.