Weather Report for February 3, 2011

A bizarre night to say the least. Extremely cold, with a temperature at sunset of only 12 deg F. By 0500 local time, the temperature had dropped to 0 deg F, the coldest that I've ever observed in. Fortunately, the wind stayed pretty calm for most of the night. However, the cold temperatures played havoc with the equipment. Dome rotation was exceedingly slow, sometimes taking 5 minutes to move between objects. In fact, the last 40 minutes of the night were lost as the dome could not be rotated as the teperature hit 0 deg F. Worse, the aperture mechanism within SPOL had all kinds of problems being properly initialized. This caused a significant loss of observing efficiency and it was decided after midnight to abandon most differential photometry as these measurements require changing the aperture often. A single, fairly wide slit was chosen for the spectropolarimetry of most objects to avoid having to change apertures and risk the mechanism losing its indexing. So, although the sky was clear for most of the night, photometry was not obtained for the objects observed during the last 4 hours of the night. The seeing was terrible all night (2-4 arcsec and usually >3 arcsec), necessitating the use of fairly wide slits for the spectropolarimetry.

Just after 2200 local time, a thin cloud cap rapidly (within just a few minutes) formed over the mountain that produced a few flakes of snow and forced a very quick dome closure. The cloud cap vanished as quickly as it had appeared and operations resumed after about 40 minutes. The forecast calls for nearly as cold a night tomorrow, so it may be slow going again.