OR 11/24/14: Lake Sonoma
by Steve Gottlieb
|
With sunset now before 5:00, astronomical twilight ended by 6:30 and a thin crescent moon set shortly afterwards. With the early nightfall, I was able to quit by 1:40 and still observe a full 7 hours! Conditions stayed clear, calm and cool, with pretty good seeing and variable transparency. The only issue we had was dew started forming after midnight and started to make things a bit moist. One small project I've started is to reobserve NGC galaxies that have faint companions, which were previously not seen in my smaller scopes. -- Steve Gottlieb |
|
NGC 161 is fairly faint, fairly small, oval 4:3 SSW-NNE, fairly high surface brightness. It contains a small bright nucleus that increases to a stellar point. A
mag 12 star is 1.2' N and a mag 12.5 star is 2' SSW. Located 6' SE of mag 8.8 Lewis Swift discovered NGC 161 in the fall of 1886 with the 16" refractor at the Warner Observatory in Rochester, N.Y., but missed IC 1557. Herbert Howe discovered IC 1557 in 1899, using the 20-inch refractor at the Chamberlin Observatory in Denver. Most modern sources incorrectly equate NGC 161 with IC 1557.
NGC 262 is moderately bright, small, round, dominated by a high surface brightness core that increases to the center, very low surface brightness halo, ~25" diameter. LEDA 212600 is just 1.2' E and appeared very faint, very small, round, 10" diameter, too faint (V = 15.4) for any details. Lewis Swift discovered NGC 262 in September 1885 at the Warner Observatory, though he missed the companion just east. As of January 1991, this Sy2 galaxy, which
resides at a distance of ~200 million light years, was the second largest known galaxy, spanning 1.3 million l.y. (S&T: July 1987, page 9). A large H I halo may have been
produced by the interaction of NGC 262 and
This giant HII complex in M31 appeared faint, small, elongated 3:2 or 5:3 NW-SE, ~15"x10". A few times a stellar point was noticed at the edge. On the SDSS there
is a mag 16.5 star (probably foreground) just 12" south. Located 13.5' W of the center of
This OB association in M31 is situated at the extreme northeast end of the galaxy, 1.2° from the center. At 200x, three HII complexes in a NW-SE string could be
detected. C372/373 at the southeast end is the brightest and appeared faint, small, round, ~12" diameter, slightly brighter stellar point at center. On the SDSS, C372/373 this is
a group of several HII complexes and I was probably picking up the combined glow of the two northern knots. Just 1' NW and 2' NW are fainter C378 and C381. C378 was extremely
faint and small, round, 8" diameter, only occasionally popped. C381 was initially seen fairly easily at 200x, forming the southwest vertex of an equilateral triangle with two mag
11/12 star. But then I had a difficult time reacquiring the small, extremely faint 8" glow.
NGC 523 = Arp 158 appeared fairly bright, moderately bright, very elongated 7:2 ~E-W, ~1.1'x0.3'. This disrupted galaxy (or merger) appeared very asymmetric, widening a bit at the east end and tapering slightly to the west. A small, relatively bright knot (HII complex or core of companion?), ~10" diameter, is at the east end. An easily visible mag 14-14.5 star is embedded at the west end. The main body, which extends ~40" from the knot to the star, is fairly thin and only very weakly brighter in the center. With careful viewing, a very faint narrow plume extends west of the main glow. Heinrich d'Arrest, observing in 1862 with the 11-inch refractor in Copenhagen, noted "Double Nebula, F, S, both very near". Although Dreyer only assigned a single
NGC number, d'Arrest apparently resolved the knot at the east end.
NGC 777 is bright, moderately large, elongated 4:3 NNW-SSE, sharply concentrated with a very bright rounder core, ~0.9'x0.7'. Two fairly bright stars are in the
field to the south, mag 9.3 William Herschel discovered NGC 777 on 12 Sep 1784, but missed (as well as John Herschel) NGC 778. Truman Safford found
NGC 931 is moderately bright and large, thin edge-on 5:1 WSW-ENE, 1.5'x0.3', brighter core, sharp stellar nucleus. LEDA 212995, a very close (physical) companion, is at the north edge just 18" from center. At 375x, it was seen as an extremely faint and small glow, ~6" diameter. Heinrich d'Arrest discovered NGC 931 (a Seyfert galaxy) in 1865 with the 11-inch refractor at Copenhagen, but of course missed the faint companion. LEDA 212995 was not catalogued by the various galaxy surveys in the 1960's and 1970's that were based on the POSS. I'm guessing a 16-inch will be necessary to clearly identify the companion.
This class XII Globular (lowest concentration class) was picked up at 200x as a faint, large, low surface brightness glow with a very weak concentration, 4'-5' diameter. At 375x, a few resolved stars shine steadily and quite a number pop in/out view consistently. Perhaps two dozen are intermittently resolved, though too lively (particularly with averted vision) to count reliably. These are the brightest red giant members and range from mag 15.5 to 16+. William Herschel, who discovered NGC 7492 in 1786, described this cluster as "eF, cL, iR. By changing and wiping the eye glasses, I saw it with both so as to leave
no doubt. 5 or 6' dia." John Herschel also found it "eF; vL; 2 or 3'; the faintest thing imaginable." NGC 7492 is certainly among the faintest NGC globulars -- at least in terms
of surface brightness -- though
This Pisces trio fits in a 5' circle. At 375x,
|
