Thin scattered cirrus started moving over the observatory a few hours before
sunset. The first half of the night was reasonably productive despite the
cirrus and very bad seeing episodes during the first few hours. The seeing
sometimes reached 5 arcsec or more, but eventually calmed to 1.5-2 arcsec.
However, the cirrus became much worse by 2300 local time and slowed
operations by a significant amount. By 0100 it was impossible to continue
and no breaks in the cloud cover appeared for the remainder of the night.