This night marked the end of the record-breaking cold snap in southern Arizona. The temperature was quite moderate throughout the night, hovering at just above freezing. This is about 35 degrees F warmer than two nights ago. The night was photometric up until about 0200 local time when thin cirrus arrived from the north. The cirrus worsened as dawn drew closer.
With the warmer weather, both the dome and SPOL behaved much better that during the previous nights. The aperture wheel in SPOL operated normally and the larger slits could be employed for photometry. Photometric data were obtained until the cirrus arrived and spectropolarimetry continued until dawn, being only slightly hindered by the light clouds. As with the previous nights during the campaign, the seeing was poor and highly variable (2-3 arcsec), but stabilized late in the night to 2 arcsec or better.