Lake Sonoma 2/28/08 Abell 347, 779

Carter Scholz

I had to drop my daughter in Marin at 5 PM and pick her up after 10 PM, so rather than make two round trips from Berkeley, I went on to Lake Sonoma. I arrived after 6:00 and set up my Highe-style 12.5" at the east end of the lot, where the horizons are best. Thin cirrus to the north and west, and visible ground-level haze, but overhead looked clear and transparent.

Another car pulled in and parked at the west end of the lot. I walked over and met Kent Brown from Santa Rosa, who was setting up his 12.5" Obsession. We chatted on the theme of how nice it was finally to have some decent observing weather. As it darkened the Gegenschein reached a good 45 degrees up from the western horizon, a few low clouds dark against it. Seeing was good, with five stars immediately visible in the Trapezium at 72x before it was fully dark.

My targets were galaxy clusters Abell 347 in Andromeda and Abell 779 in Lynx. I had tried the latter from Del Valle but could see nothing but the central galaxy, 2832. Lake Sonoma skies are typically about one magnitude darker. The SQL meter confirmed this, reading 21.3 (as against 20.3 at Del Valle). Also, I was now better equipped with annotated DSS/HST plates.

Abell 347 is roughly halfway between Almaak and M34. NGC 891, a large showy edge-on with a dust lane neatly bisecting it, is about 20' NW of a mag 7 star that was my first anchor. Most of the action is within half a degree of this star. I glimpsed an edge-on between it and a mag 8 star 20' south -- 898. A little chain 10' long of three unequally spaced mag 10 stars lead east from the mag 7, and these became my next anchor. 10' south of the eastmost star is 910, the (ahem) "brightest" galaxy in the group, faint, round. It took a while before I saw 911, very close to the east star in the chain. Then 909 and 906 became apparent in a NE-trending chain crossing the chain of three stars. Not much detail. Went back to 910 to see if I could spot nearby 912. Very doubtful -- a little hopeful blur less than 20% of the time with averted vision.

Abell 779 is near alpha Lyncis. A chain of five mag 10 stars, more or less linear, starts south of alpha and heads SW. The brightest galaxy here (still pretty faint), 2832, is about 15' south of the last star in this chain, close to a double pair of stars reminiscent of eps Lyrae. There are three galaxies here, very close together. I couldn't separate 2831 from 2832, and barely glimpsed 2830, an edge-on. Moving west, 2825, another edge-on, kind of blinked in and out, and 2826 to the south did the same more emphatically. An interesting effect. I wonder if edge-ons are any easier because of their geometry.

There seems at least to be less chance of mistaking a faint star for one. These were definitely edge-of-detection, but the orientations matched the DSS. Did not see 2834, 2839. (BTW, on the HST Phase 2 plate, there is a kind of faint fuzzball about 6' S of 2832 about 3' in diameter. Does anyone know if that's anything, or just a plate defect?)

I finished about 9:30 with Saturn, showing a few bands and a striking arrangment of moons -- Tethys and Encelade just off the rings on opposite sides, and Mimas very close to the NE limb. It had grown damp; temp was 48F and humidity 80%. Said goodbye to Kent and the friend who'd joined him. Fog was spilling across 101 on the drive south and Berkeley was socked in when I got back. Nice night. Nice to get out again.