Witnessed a spectacular sunset because of all of the cirrus in the sky. Observed through the cirrus, which moved off by about 2 hours into the night. The sky was generally clear from then until about 0200 local time when more thin cirrus moved in from the northwest. Again, polarization measurements were not greatly hampered by the thin clouds. Some of the photometric measurements, however, may have to be thrown out. The night was warm and calm with good seeing (1-1.5 arcsec).