The decision to open or close the telescope is the responsibility of the Telescope Operator(s).  They are the senior staff member(s) on-site and responsible for the facility.  Their decision will be based on their experience at LDT and judgement of the site conditions, and is final.

The guidelines given below are there to help them make their decisions, and to give you a sense of what kinds of things they are considering, but they are guidelines, not hard and fast rules.  Safety of people and the equipment is an overriding concern.

Here are the basic criteria that your TO will consider when opening or shutting down operations:




If the TO judges that it is unsafe to operate.


ambient relative humidity ≥ 85%

M1 relative humidity ≥ 80%

condensation in the dome


sustained wind ≥ 11 m/s (~25 mph)

gusts ≥ 16 m/s (~36 mph)

strong smell of smoke outside &/or high particulate counts


ANY visible/measured precipitation in the area

FogVisible fog on-site, this may require a flashlight at night.
Ambient Temperature> 30°C or < -20°C

The TO will judge when it is safe to reopen the telescope, generally at least 10 minutes after conditions have become acceptable again.

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