Dew problems and Death Valley observing

by Bill Feiereisen


Last night my backyard offered up some of the best seeing that I seen in a long time. Jupiter was phenomonal for seconds at a time showing as much detail in my 8" newtonian as I've ever seen. However, the "seconds at time" degraded pretty quickly with dew. After a time the scope looked like it had been sprayed with the garden hose. The eyepieces would dew over in seconds, but more disturbing was the secondary. It would also dew over. I think part of it comes from my breath and the dewpoint. I can fix the eyepiece with a hairdryer, but am wary of warming the secondary for fear of destroying the temperature adaption of the mirror and thus the wonderful image quality. Any ideas? ... Bill

ps: Just spent six days camped in the backcountry of Death Valley with three really good nights. No dew there! It was dark to the horizon in almost all directions (except Beatty and Trona). I spent hours just bouncing around from sight to sight. The showcase sights like M42 and the Pleiades had incredible detail. There was very obvious nebulosity around all of the bright members of the Pleiades and delicate detail in M42 that occupied me for quite some time. I picked off a number of planetaries that have been on my list. We were camped at lat. 36 degrees, 19 minutes and had a direct view of the southern horizon. For a couple of minutes each evening Canopus would poke its head over the horizon (dec: -52d, 41m). Big 4WD trucks are great. They carry campers and telescopes to extremely remote locations and allow fantastic observing while living in relative comfort. No neighbors for miles. I've noticed that Annette sometimes gets nervous on the way to our campsites. You know, locked down in 4wd low range and grinding up the mountain by some precipitous drop off. Now why would that be? :-)