Light cirrus moved over the site during the first half of the night. Although not photometric, the night was very productive and polarimetry was not greatly slowed until after 0200 local time when the much thicker cirrus seen to the west and north in the weather image started to move in. Operations ground to nearly a halt by 0400 and a few late-night targets could not be observed. The seeing was generally between 1.5 and 2 arcsec.
