How was the seeing at the Peak last night?

by Jay Reynolds Freeman

NB: "Last night" means "Friday, May 7".

I went to the Peak Friday evening with my 6-inch f/8 Astro-Physics refractor. Seeing between dusk and the end of twilight was so-so -- Mars showed little detail -- but there was no problem doing deep-sky stuff. Fog on the coastal plain helped a little, but was not very thick. Unfortunately, the vagaries of breeze brought the fog around the back of the mountain and up to the edge of the ranger's yard, where I was set up, at about 10 PM. Conditions got very humid very rapidly, and I decided not to try to fight it, so covered my optics. Conditions had not changed by 11:30, when I left. The sky was not blocked by fog, but relative humidity was around 90 percent. (I have a portable thermometer and relative humidity meter from Radio Shack -- fun to watch what is happening -- things went from about 10 C and 55 percent to about 3 C and 90 percent in less than five minutes.) Other observers who kept operating -- sky not blocked, remember -- reported very poor seeing, which made sense, for the boundary between cold, wet, air and warmer, dryer stuff must have been only a few tens of meters above us, and must have been oscillating as the fog sloshed back and forth.