The telescope dome shall be closed when any of the following weather conditions occur :
- Wind speed > 15 m/sec
- Humidity > 90%
- Temperature within 2 deg of Dew point
- Dew on the dome The operator will check the dome in person when there is reason to believe that condensation may occur
The telescope shall not be pointed into the wind when the wind speed is between 12 and 15 m/sec
Note: The telescope operator will make the decision to close the dome as necessary. The visiting observer should acquiesce with the decision since the point of the whole exercise is to protect the telescope from damage. At any rate, in case of a disagreement the dome should first be closed and subsequently the visiting astronomer may take up the issue with the support astronomer and finally the La Silla co-ordinator - though it is highly unlikely that the decision will be altered.
The dome may be re-opened if weather conditions improve and stay below the operating limits for at least 30 minutes. This waiting period is particularly important in case of humidity.