Fremont Peak, Nov. 1, 2003

by Peter Natscher


LocationFremont Peak, Ranger Row
DateNov. 1, 2003
Temp./RH5:15pm, 48/85%; 10pm, 40/95%.
ConditionsNo wind, partly cloudy, bright moon with haze.
Transparencymag. 5.5 (Cygnus-Cassiopeia)

First Light for 20" f/4.29 Starmaster Dob.

I was set up in Ranger Row to first light my new Starmaster 20" Dob. Ray Duval, a new TAC member, was nearby observing with his new 8" Cass. The mechanics in my new 20" Starmaster Dob checked out fine in the 3 hours that I observed with the scope. The seeing turned out to be less than what this size aperture requires for doing any meaningful optical testing of the 20" Zambuto with a 98.5 Strehl ratio. I don't believe that the 20" mirror ever settled well enough for testing. The air above exhibited a fair amount of turbulence even though it was still at our 2,800 ft. elevation. Out of focus stars showed heat rising off the primary mirror most of my observing time, 'til 10pm. Star images through my eyepiece at all powers (75X-350X) showed fair amount of turbulence above. Inside/outside focus patterns looked good but no diffraction rings could be gotten. The finer optical testing will have to wait for a better night of seeing.

Dew started forming on our scopes as early as 9pm and Ray's 8" Cass. dewed up so much that it put him out of action soon thereafter. My 20" Dob was externally wet but dry optically in the 40 degree temp. air. I did have an easy look at a few mag. 12-14 galaxies, planetaries, and brighter open clusters along the Milky Way in the darker part of the sky in Perseus, Cassiopeia, Cepheus, Draco. Even in the bright sky, NGC 1023 (a fine large nearly edge-on galaxy in Perseus) looked very nice and M57 still showed its central star and its many mag. 14.5-15 surrounding stars. There was a surprising level of moisture in the air characterized by a bright haze over much of the sky by the moon. I packed up by 10 pm after doing as much as I wanted to do in checking out the scope, limited by the weather conditions. I can't wait to get this scope out again in a darker sky where it should excel.

Up the observatory hill, a few FPOA members opened up the observatory and were operating "The Challenger" for their guests. I spent an hour there amused by observing the confusion among operators and managed to get a few good low-power views of various open clusters.