Lake Sonoma 9/3/08

Steve Gottlieb

After sunset I was curious if we could snag the tight triangle of Venus/Mercury/Mars. From the spot we set up, the western horizon was a bit obscured (we're talking just a few degrees), so although Venus was easy enough I knew it would be very difficult or impossible to spot Mercury. Greg said "no problem" and just picked up his 12.5" ultralight and easily walked with it in hand to a more favorable spot higher in the Lone Rock parking lot. At this point Venus was perhaps 3 degrees off the horizon and Mercury even lower, but Greg immediately picked out a nearby "star" in his finder and one look in his scope confirmed it was Mercury, just 2 degrees from setting! Knowing the exact location, we were both able to glimpse it naked-eye but it took some effort. Mars was much fainter, but 4-5 degrees in elevation. The 3 planets are now within 3-4 degrees of each other. After carrying Greg's scope back the sky was still darkening so we both gawked for a while at the knotty detail in Jupiter's belts and the feathery festoons.

The last couple of months, I've been making a little mini-project of tracking down MASH planetaries that were discovered in the past couple of years (http://tinyurl.com/58khqz) and I was able to nab a couple more from Lake Sonoma. As these objects were only announced in a 2006 astronomical journal paper, you won't find them on any amateur software or atlases. But that's what makes the hunt fun -- knowing you're one of the first to ever have a look. Here are the details --

PPA J1855-2328 = PN G012.1-11.2
18 55 04.9 -23 28 12
Size 20"x18"
This MASH planetary was picked up at 300x as a very faint glow encasing a close, faint double star (oriented SW-NE). The contrast was only weakly enhanced adding a NPB filter, but the superimposed stars (the NE star may be the central star) are dimmed out and remaining is a 15" irregular disc with a better-defined outline. The best view was at 450x unfiltered. At this power, the double was easily resolved and the SW star was clearly situated at the SW edge of the glow.

PHR J1911-1546 = PN G020.9-11.3
19 11 04.4 -15 46 07
Size 153"
At 115x and UHC filter, this MASH discovery appeared as an extremely faint, large disc, ~2'-2.5' in diameter, though the edge of the halo was not sharply defined. A mag 11 is close off the NW side and a line of 3 mag 13-14 stars lies ~1.5' SSE. Also viewed at 175x using a NPB filter.

A couple of my favorite galaxies for the night were barred spirals -- NGC 6907 in Capricorn and NGC 6217 in Ursa Minor. Both showed the central bars and some of their arm structure.

NGC 6217
16 32 39.3 +78 11 54
V = 11.2; Size 3.0x2.5; Surf Br = 13.2
This barred spiral displays subtle spiral structure and is a fascinating object. At 280x, the main portion appears to be a large central bar, 1.5'x1.0', oriented NNW-SSE. An unusually bright stellar nucleus or a superimposed star at the center punctuates the bar. An extremely faint star is close SSE along the central star. Off the N end of the bar is a faint appendage or arm is attached that gently curves to the SE and increases the overall dimensions to 2'x1.5' . Off the SSE end of the bar, some very weak haze extends to the southwest (beginning of an arm).

NGC 6907
20 25 06.7 -24 48 32
V = 11.2; Size 3.3x2.7; Surf Br = 13.4; PA = 46d
Beautiful view at 280x using an 8mm Ethos. A large 2' "bar" is oriented E-W with a broad, weak concentration but suddenly rises to a very small, bright core and faint stellar nucleus. On the east side of the bar, a spiral arm is attached that hooks directly to the north and just begins to sweep clockwise around on the north side of the galaxy towards the west. There appears to a brightening (faint knot) near where the arm is attached to the bar. Off the west side is faint haze on the south side, but the arm structure is very weak. A mag 11.5 star lies 2.8' due E of center on line with the central bar.

Greg's already mentioned a few other great fascinating objects we both looked at in each other's scopes (Sh 2-157, NGC 7538, NGC 7510), so I'll throw in an interesting Palomar globular...

Palomar 12
21 46 38.8 -21 15 03
V = 11.7; Size 2.9
At 283x, this low surface brightness globular was immediately evident as a very faint, moderately large hazy glow, ~2.0' or slightly larger in diameter. Located just N of a bright trio of mag 12 stars (two of these form a 20" pair). Three faint stars (nearly collinear) are resolved, one at the NW side and other two to the SE, near the center. This object has been catalogued several times as a dwarf galaxy, so it may show up as a galaxy on some amateur sky software.

Other than having to teach a calculus class a few hours after arriving home (I had to fake it with my students that I was awake!) in the morning this was really enjoyable adventure.

-- Steve