Weather Limits
Observers should be aware of the following conditions which
limit or prevent operation of the telescope.
Several weather monitors are available for various locations on
Mount Hamilton.
Refer to Lick Observatory Weather
to get real-time readouts of the local weather conditions. It is the
responsibility of the Observer to monitor the weather and ensure that the
telescope is protected from the elements so that no harm comes to any
of its systems.
Note that these limits are only guidelines.
Observatory staff members may instruct you to close the enclosure if they
deem it necessary to protect the telescope.
Wind Limits
| Average (MPH) | Persistent Gusts (MPH) |
| Into Wind | 35 | 40 |
| Crosswind | 40 | 45 |
| Downwind | 45 | 55 |
Exercise caution using windscreen as
windspeeds approach limits.
If you have closed the enclosure for wind, a reasonable rule of thumb is to
wait 20 to 30 minutes after the winds have subsided to re-open the
enclosure. If in doubt about when it is safe to reopen the enclosure after a
wind closure, consult the Shane Telescope Operator.
Humidity
- 94% relative humidity, or
- when dew sensor alarm sounds above 0 degrees centigrade, or
- as necessary to exclude moisture from the dome.
If you have closed the enclosure for humidity, a general rule of thumb is
to wait until the humidity has dropped well below the limit and things
are drying out (e.g. humidity is 85% or below for 30 minutes) before
reopening the enclosure. If in doubt about whether conditions have dried out
enough to safely open the enclosure, consult the Shane Telescope Operator.
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 Enclosure
If snow has accumulated on the enclosure and not been shoveled, keep the
enclosure closed to prevent snow from falling or blowing onto the
telescope. Contact the Shane Telescope Operator or a Support Astronomer
if you are unsure of the state of the snow on the enclosure.
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 a danger of a strike. The Shanen 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.
Support Astronomers, sa@ucolick.org
Last modified: Mon Aug 17 00:10:53 PDT 2015