Weather Limits3-meter observers should be aware of the following conditions which limit or prevent operations of the telescope.
Temporarily Enhanced Limits Imposed 2020-10-01, Removed 2021-01-07The temporary closure limits imposed in the aftermath of the 2020 SCU Lightning Complex wildfire have now been lifted. We have thus returned to the pre-fire limits for wind, humidity, and dewpoint.
Current LimitsNote that these limits are only guidelines.
The decision to open or close the dome is entirely at the discretion of the telescope operator.
|Average (MPH)||Persistent Gusts (MPH)|
Humidity94% or at the telescope operator's discretion based on blowing fog, condensation on dome and handrails, etc..
Airbourne Particles/AshEnclosures must be closed if airborne particles (e.g. ash from forest fires) are deemed a threat to the optics. A particle counter resides inside the Shane enclosure and measures particles 0.3 microns in size and 0.5 microns in size.
A second particle counter resides outside the APF dome and measures particles 0.3, 0.5, 0.7, 1.0, 2.0, 3.0, 5.0, and 10.0 microns in size.
The interior particle counter responds to outside changes, even when the enclosure is closed. The following threshold values (adopted 2013-08-05, updated 2021-03-04) apply (even when the Shane enclosure is closed):
||0.3 micron||0.5 micron||0.7 micron||1.0 micron||2.0 micron||3.0 micron||5.0 micron||10.0 micron|
Snow on DomeIf 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.
LightningIf 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 a danger of a strike. Telescope operator can stop observations to shutdown critical electrical systems as his or her discretion. Wait at least 30 minutes after the last audibule thunderclap before declaring the storm passed and resuming operations.
Last modified: Wed Mar 10 15:11:44 PDT 2021