by Robert Sheaffer
Last night I went on my first dark-sky trip since moving south. The San Diego Astronomical Society maintains a dark-sky site in the desert at Tierra Del Sol, about 50 miles east of my home (see http://www.sdaa.org/SDAAEvents/sdaa_tds.htm). Public star parties are held twice a month, on the Saturday nights closest to Third Quarter, and to New Moon.
I drove out last night, and set up my Celestron 11" GPS in one of the public viewing areas. There were more astronomers with scopes than members of the "public." The area is at elevation 3600 ft., and very dark. To the west, a patch of illuminated fog indicated the location of San Diego. To the east, a smaller region of was probably El Centro and/or Mexicali (the site is quite close to the border).
I began working galaxies in Leo and Virgo. Two other galaxies were visible in the field with M105, NGC 3384 and 3389. When I mentioned this to the fellow next to me, who had set up a 20" Obsession (!!), he (not to be outdone) wheeled over to the Virgo cluster and showed ten galaxies in the same field! M51 in the Obsession was truly dramatic.
M65 and M66 in Leo showed wonderful detail in the 11". Not just fuzzy blobs, they actually revealed structure in the core and the arms. M60 in Virgo revealed its spiral arms, as well as its conspicuous companion galaxy, NGC 4647.
The biggest surprise was the giant globular Omega Centauri. I had seen this from Monte Bello several times. From there it barely clears the horizon. It appears as a large smudge, if you're lucky enough to see it at all. With the 4 1/2 degree elevation advantage gained by going south, the difference is dramatic. In the 11", Omega Centauri is properly seen as a giant globular that practically fills a low-power field. It was fully-resolved all the way across, and has the same kind of streams of stars moving outward from the center that you see in M13.
The air was more moist than I had expected, for the desert. I did not have my best dew shield with me. Naked-eye limiting magnitude was not much more than 5.5. Around 11:00, everything started getting very wet. I imagine that in the summer, when daytime temperatures at the spot climb to around the boiling point of water :), the nighttime transparency will be even better.