The bulk of the clouds forecast to move in waited a bit to envelop Kitt Peak and so observations could be made for about the first six hours of the night. There were some clouds at the start of the night and these prevented a couple of far western targets from being observed. The sky was generally clear, although the mountain formed some thin clouds from time to time, until nearly 0200 local time when the clouds thickened enough to end observations. In all, a dozen blazars were observed in seeing that was typically 1.3-1.5 arcsec. There were short periods when the seeing blew up to over 2 arcsec. By 0400, light rain had started and the wind was howling out of the east at 30-40 mph.
A major milestone was reached tonight with the last blazar observed before the
weather halted operations. AO 0235+164 earned the distinction of being
the 10,000th target measured for linear polarization during this program supporting the
Fermi Gamma-ray Telescope. On 2008 October 3, Mrk 501 was the first blazar observed for the
program. It has been quite a journey.