Science Operations

Guidelines for Operating

Please be aware that the below are GUIDELINES; operations and opening or closing of the telescope enclosure is at the sole discretion of the Observing Support Associate (OSA/TO). His/her decision may encompass many mitigating and complex factors. For the safety of the telescope, enclosure, and personnel, OSA authority regarding weather closure is final and absolute during nighttime operations.

Main Shutter Doors

  • Winds:
    • Close if Maximum sustained Wind Speed exceeds 20 m/s (45 MPH) or gusts to 22 m/s (50 MPH). ¬†For the purposes of these guidelines, it is assumed that the higher of the two anemometer readings from the roof of the enclosure represents the true wind speed.
      These values were initially determined based on the SMT anemometer. The present wind limits are based on telescope shake, blowing oil droplets, adaptive secondary safety and building survival.). Close if you are getting more than 1 gust above the limit in 6 minutes. Reopen if there have been no gusts above the limit for 18 minutes. Also monitor the enclosure-telescope encoder values on mcspu for excessive fluctuations; > ~0.5 deg which indicate wind shake of the enclosure that means it is time to close.
  • Humidity:
    • Close when Humidity exceeds 95%, and reopen when Humidity is less than 90%. To open, the exterior surface of the rotating building should be dry and not dripping water. The railings on the patio make a fair substitute hygrometer (if the railing is wet, the shutter doors should be closed).
  • Severe Weather:
    • Close if there are any rain showers or thunderstorms within 30 miles (48 km).
    • Close if there is blowing snow, rain, dust, ash or pollen. These can be detected in the beam of a normal flashlight.
    • Close unless some stars visible to the naked eye. (Clouds have not more than 6 magnitudes of visual extinction).
  • General Mirror Safety:
    • Stay closed unless Temperature Difference between Primary Mirror glass therms and WS ambient is less than 10 degrees C. (Open vent doors and run mirror ventilation to bring mirrors into better equilibrium if other conditions permit.) Always have mirror ventilation running before opening shutter doors if a temperature difference of more than 5 degrees C exists.
    • Remain closed unless there is no substantial amount of snow or ice on shutter door joints/seals which could fall or blow into the telescope. (Stable ice on the shutter door panels is OK if the seals are clear.) Ambient temperature must be above -20 degC. (Don’t even drive the closed enclosure around if temperature is below -20 degC, and leave the telescope parked at zenith.)

Ventilation Doors

  • No snow accumulation on vent door sills before opening them.
  • No blowing snow, rain, dust, ash or pollen.
  • Close ventilation doors to 1/4 when wind exceeds 6 m/s. Close ventilation doors when wind exceeds 10 m/s. (These wind limits assume the main shutter doors are open. If main shutters are closed, then the ventilation doors may follow the main shutter wind limits.)
  • Do not open side vent doors if the there is any chance of dripping water from the roof drain on the main shutter doors.
  • Ambient temperature must be above -15 degC. (Pending a fix to the vent door drives that will allow them to operate like the shutter doors.)

Adaptive Secondaries

  • The elevation observation limits are as follows:
    • The observational limit for the AdSecs is 30 degrees, below which the AdSecs will rest. Note, if the AdSec rest below 40 degrees elevation during an observation the telescope must be slewed to above 40 elevation to Set the thin shell. The observation can then resume below 40, down to the el limit.
    • If an observation requires an elevation limit below 30 degrees, please send the request to in advance or your run.
  • Winds:
    • Note that winds on the AdSecs are not the same and winds on the enclosure. The enclosure itself and other factors provide shielding to the AdSecs. Changing orientation can often change the winds recorded on the adaptive secondaries
    • Winds on the AdSec of 5m/s or more will enable TSS. The AdSec should remain set and will not be available for diffraction limited use above 5m/s gusts. Users are encouraged to try a different telescope pointing, out of the wind.
    • Telescope must be moved or closed if wind gusts of 10m/s on the AdSec are seen.

ARGOS Laser Operations

  • We can not perform ARGOS observations below 35 degrees in elevation. This is a hard limit imposed by the Federal Aviation Administration.
  • All targets must be provided in advance for approval and clearance. Please be aware that we are limited, on a target by target basis, by satellite shuttering windows imposed on us by the Joint Space Operations Center. A preliminary version of these shuttering windows will be available approximately 1 day before the run. However they may be changed at any time. We can not guarantee in advance that any given target will be available for observation on any given night. On rare occasions, ‘blanket closures’ can be announced that prevent us from propagating the lasers in any direction for part of a night. Unfortunately, these closures are beyond the control of the observatory.