by Robert English
Ken Frank, Mark Mickels, Marc Bruvry, Darrell Lahmann, and others joined in observing comet Machholz grazing a field star. Shortly thereafter, heavy dewing began affecting telrads. We continued observing various targets and enjoying very good seeing with little scintillation. A layer of low haze/for helped to cut sky glow from SF, and once the moon set, the stars looked like they were painted on the sky dome.
Soon however, the first SCT in the group (didn't have a dew shield) reported corrector plate dewing. I noticed that the dew on our vehicles had frozen. Mark Mickels reported his eyepieces were fogging. Darrell's 12", which had a dew shield, frosted over. My secondary (no dew heater on a truss scope) dewed up.
By 8:30, we were improvising wrapping chemical handwarmers around our secondaries to keep them clear. This proved ultimately unsuccessful. The breeze had gone and temperatures were now below freezing. The only scopes still in operation were traditional newts (XT-10, and an aluminum tube ATM scope). Ultimately, the XT-10 was shut down due to secondary condensation by 9:30.
So our first January observing session taught us a valuable lesson about cold weather observing: You can't see when you can't see. Many of us will be researching dew removal stategies in the coming days, and we hope to be ready for February's event.
It was a wonderful night for observing, and a welcome break from the miserable weather we'd been having.
The SFAA Mt Tam events had been held from spring through autumn in the past, and condensation/frost had never been much of a problem, but now with our extended calendar, we welcome the chance to adapt to year-round observing.
Give me good friends, fine telescopes, excellent seeing, dew removal and a bag of Chee-toh's and I'm happy.
Clear Secondaries!
Posted on sf-bay-tac Jan 13, 2005 09:33:22 PT
Converted by report.pm 1.2 Jan 27, 2005 20:56:18 PT