Steve GottliebIt's been over 3 weeks since I ventured out to Willow Springs with several other bay area observers, but who knows when the next clear moonless night will occur; so a little reminiscing seems in order. I set up at Kevin Ritschel's Deep Sky Ranch along with Bill Cone, Bob Jardine, David Cooper, Elisabeth Oppenheimer and Mark Wagner. Kevin's 33-inch was out of commission this night due to collimation problems and it felt a little odd not to be observing in the shadow of that monster.
Conditions were very good for this time of year - dark, transparent, dry and no wind though the seeing was a bit soft. In the middle of the night I had no problem spying the faint gegenshein, nestled between the Pleaides and the Hyades, though it was not quite as evident as I've seen it before from Willow. More challenging than the gegenshein is tracing the extremely dim zodiacal band along the entire ecliptic. Between 2-3 AM after folks had stopped observing, I started to trace the zodiacal band east across the Milky Way and Bob Jardine and I definitely could see the glow down past Regulus (towards Saturn). It was hard to follow looking west as it faded out around Aries, but still arched over 75% of the sky.
Let's wind the clock back a few hours when Bob and I compared views of the local group dwarf, Wolf-Lundmark-Melotte (WLM system) in our scopes. WLM is a difficult, low surface brightness dwarf in Cetus, spanning 10'x5', but in good transparency was picked up without much difficulty in my 18-inch Starmaster while sweeping at 115x.
The skies seemed dark enough to go after the Sculptor Dwarf, an even more challenging local group dwarf that was discovered photographically by Harlow Shapley in 1938. To further thwart visual observers is the -33 degree declination which requires a clean, transparent southern sky. At 115x all that was "visible" was a very large, ill-defined glow, ~15'-18' diameter. The overall surface brightness was extremely low and it was difficult to trace the halo as it faded into the background sky. A couple of other folks confirmed the observation, though Bill seemed to think we might be using averted hallucination.
To continue on the local group dwarf theme, I also took a look at IC 1613 in Cetus, a large irregular glow just east of a mag 10.5 star. All three of these objects are relatively nearby but difficult to view and outside the local group would be impossible to detect. In terms of numbers, though, these low mass objects dominate the universe.
About 45' to the east of IC 1613 is a rich galaxy cluster, AGC 147. I was able to snag 5 members of this cluster. The distance comparison is mind boggling - IC 1613 is a cosmic neighbor at 2.4 million light years, while AGC 147 resides 625 million light years away!
A little later in the evening I started working on some galaxy clusters with Mark, using detailed Megastar charts to pull in fainter and fainter members. Although we were both observing at our scopes, we talked back and forth giving directions and descriptions of galaxies that were often at the limit of visibility.
The NGC 80 group is near the midpoint of a line connecting two stars in the Great Square - Alpheratz (Alpha And) and Algenib (Gamma Peg). The cluster contains 10 NGC galaxies (79, 80, 81, 83, 85, 86, 90, 93, 94, 96) and a sole IC member (1546) along with a slew of dim galaxies catalogued in Megastar as MAC listings and more formally in the 2- Micron All Sky Survey (2MAS). By working together and confirming observations, we were easily picking up galaxies with a (blue) magnitude of 16.5 and a few as faint as mag 17.1 2MASX J00214701 +2219591.
Next up we tackled AGC 400. This cluster contains at most 1 NGC member - NGC 1128 at the center of the cluster (Megastar and others list this galaxy as MCG +1-8-27). This was the first one we viewed and at first I just logged it as "faint, small, elongated 3:2 N-S, 25"x18"." But then I realized this was an extremely close contact pair oriented N-S with two tangent knots just 15" in diameter - a tiny dumbbell galaxy! A half-dozen extremely faint galaxies swarm nearby within a 6' radius and moving out to about 20' from the core of the cluster we picked up 20-25 members.
At this point, I think our eyeballs were both pretty exhausted and I didn't last too much longer before just admiring the night sky naked- eye - bringing me back to the gegenshein and zodiacal band observation.
2010, July 10 - 14
Frosty Acres Ranch
OMG! Its full of stars.
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