User's Guide to the Shane 3-m Telescope

Table of Contents

Diagonal Mirror
TUB Rotation
Arc & Flat-field Lamps
trouble report
Target Of Opportunity (TOO)
Remote Operations
Data Archive
Mt. Hamilton Homepage

Weather Limits

3-meter observers should be aware of the following conditions which limit or prevent operations 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
Exercise caution using windscreen as windspeeds approach limits.


94% or at the telescope operator's discretion based on blowing fog, condensation on dome and handrails, etc..

Airbourne Particles/Ash

Enclosures 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. The particle counter responds to outside changes, even when the enclosure is closed. The following threshold values (adopted 2013-08-05) apply (even when the Shane enclosure is closed):

0.3 micron 0.5 micron
Warning 12000 800
Closure 17000 1000
Particle counts must remain consistently below the closure thresholds for at least 30 minutes before (re-)opening enclosure can be considered.

If in doubt, contact the Shane telescope operator (8-0652).

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.


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 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: Mon Aug 17 00:41:43 PDT 2015