An isolated batch of fast-moving cirrus clouds moved over Mt. Bigelow starting
at about midnight and was a problem until almost 0300 local time. On either side
of this period, the sky was clear and a lot of work was accomplished. The seeing
during the first half of the night was very poor and variable (2.5-5 arcsec).
After the clouds left the sky, the seeing was a more respectable 1.5-2 arcsec.