Sky Condition at Paranal
The sky transparency is assessed at various times per night, with the help of the Weather Officer. For a declaration of Photometric sky conditions, observations of photometry standar stars with the Omegacam instrument (VST) or FORS2 (UT1) are currently required.
The following plots show:
- The monthly percentage of Photometric + Clear sky condition, and
- The monthly percentage of usable observing time, i.e. Photometric + Clear + Thin cirrus sky conditions
The long-term (2014-2024) of the Photometric + Clear fraction at the Paranal Observatory is 77%. And the usable time fraction is 90%.
The long-term average of the fraction of clear skies is 75% for the winter semester April-September, and 80% for the summer semester October-March.
