The sky was clear for the majority of the night with a first quarter moon and seeing that varied from 1-2 arcsec. The moon prevented a few of the faintest targets from being observed during the first half of the night. Clouds rapidly approached the observatory from the northwest. At the start of the night, they were just crossing the Arizona border at the Grand Canyon. The cirrus arrived at just before 0300 local time and prevented further flux measurements. Polarimetry continued for the rest of the night, but at reduced efficiency. A very productive night.
