Zenith distance: < 75 degrees to avoid tipping mirror.
Relative humidity: close the dome at 95% RH or earlier
if necessary to exclude any and all moisture from the
dome. In particular be alert for sudden and unexpected
fog formation and do not leave the vicinity of the dome
if it's open without being very alert for any sudden
change in the weather. If you can see moisture in your
flashlight beam, or if wooden surfaces and papers get wet;
Wind: no explicit limit, but when leaves and twigs start
blowing in perhaps you're pressing too hard. Usually
before that happens, the tube will shake too much for
reliable observations anyway.
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
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).