The first half of the night was spectacular with photometric skies and seeing of 1.2-1.4 arcsec. Then, at about midnight the mountain range decided to produce orographic clouds in amazing profusion. This is something that I have only seen during high-humidity nights and the humidity in the dome tonight was under 50%. Furthermore, there was no evidence in the weather forecast or in the satellite images to suggest that there were any clouds within 200 miles of the observatory. Conditions started improving at around 0230 local time and the seeing held steady. Overall, this was a strange but productive night to end a highly productive observing campaign.
There is now a lengthy break in the monitoring program, since it is not
scheduled during the next dark phase of the moon. This will be the first
dark sky period missed outside of the summer monsoon season since 2009.
Observing campaign 55 will begin close to Thanksgiving over on Kitt Peak
at the Bok Telescope as
the busy holiday observing periods get started.