It was a lonely star party at Lake Sonoma last Saturday as I was surprised to
find myself the only one taking a chance with the mixed weather forecast and
poor transparency predicted by CSC (or do others have better things to do??).
Fortunately, when I arrived at just after sunset both of the main observing
lots (Gray Pine and Lone Rock Flat) were both ungated and I decided to set up
at the higher elevation of Lone Rock Flat. Conditions were quite gusty with a
chaotic mix of low and upper level clouds. Within the next hour, though, the
skies completely cleared and the wind completely calmed. I expected one or
two observers to roll in as moonset was not until 10:30, but the only
neighbors during the evening were the occasional howls of the surrounding
coyotes and an amorous couple who drove to the other end of the lot and was
not heard again.
Given the rapidly changing weather conditions while I was setting up, I was
surprised when I took a look at Jupiter with my one month old 18" Starmaster,
the seeing was quite good and at that very moment (~7:45) Europa's shadow was
just starting a transit on the extreme edge of the disc. After looking at
several doubles in the 1"-2" range, I took another look at Jupiter around
8:20 and at that moment the disc of Europa was just ending its transit and
appearing like a pimple, not yet disengaged, on the edge of Jupiter's disc.
As a few hundred (faint) spring galaxies are the only NGC objects I still
have left to observe, I immediately set to work on these as soon as the moon
drifted below the hill to the west. Even scraping the bottom of the NGC,
there are always a few surprises to spice up the evening.
N3930
11 51 45.8 +38 00 54
V = 12.4; Size 3.2x2.4; SB = 14.4; PA = 30d
This is a pretty nondescript galaxy. But John Herschel description from his
Slough Catalogue (1825-1833), didn't make sense: "A star 7th magnitude
following nearly in the same parallel, distance about 3'." Furthermore,
William Herschel stated in 1787 that N3930 was 5' South of a star 6th
magnitude. But the only bright star nearby was roughly 23' SE! Hmmm, seemed
fishy until I realized this star was Groombridge 1830, which has the third
fastest known proper motion and is traveling SE at a rate of 7.04" per year.
In the 216 years since William Herschel first discovered NGC 3930,
Groombridge 1830 has raced out of the field and scooted 25' to the SE!
18": very faint, moderately large, round. Appears as a very diffuse
ill-defined glow with just a weak concentration. Not noticed initially in
the field. Located 2.5' E of a mag 13 star which is the further south of
three collilnear mag 13/13.5 stars. Groombridge 1830, just 3' from N3930 when
John Herschel took a look, is now roughly 23' SE!
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N3280
10 32 43.7 -12 38 15
V = 14.1; Size 0.7x0.5; SB = 12.8
I was expecting to find a single faint galaxy here - with a relatively faint
V magnitude of 14.1 (blue magnitude of 15). But it was a much more
interesting knot of galaxies. In fact, the original discovery description by
Ainslee Common from 1880 with a 36-inch reflector mentions "Faint double
nebula with two stellar centers", although this object only received one NGC
number. There are actually 3 components here, although I couldn't confirm
the smallest member.
18": this is a triple system listed as N3280/A/B in the new DSFG. At 262x
there was a confused glow, ~1' diameter. Within the glow, two small knots
(N3280a and N3280c), ~0.4' and 0.3' were resolved, oriented E-W, with the
larger component on the west side (separation is 40" between centers). At
moments there was a impression of a very small and faint third component
squeezed between these two galaxies. In a small group with N3296 4.8' S and
N3297 7.1' ESE. Located 4.6' NE of a mag 9.5 star.
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N3447
10 53 23.9 +16 46 25
V = 12.6; Size 3.7x2.1; SB = 14.7; PA = 0d
The brightest component of this interacting double system (N3447 and N3447B)
was not difficult, but I wasn't sure if I caught its difficult companion. My
real quest, though, was PGC 32713 which lies 8' NE of N3447. Although it has
no other catalogue designation, this galaxy was a special target, as it is
the brightest member of a distant Abell Galaxy Cluster (ARC 1126) and has a
catalogued redshift of z = .086. This converts into a whopping distance of
1.3 billion light years! (using a Hubble constant of 65 km/sec/Mpc)
18": very faint, fairly large, very diffuse glow. Located 3' NE of mag 9.9
SAO 99342 and nearly collinear with mag 9.1 SAO 99340 8.3' SW. This
disturbed irregular system forms a close pair with N3447B = M+03-28-028 1.7'
NE. An extremely distant galaxy PGC 32713 (z = .086) lies 7.8' NE.
N3447B
10 53 29.7 +16 47 02
Size 1.5x0.8; PA = 110d
18": this low surface brightness elongated companion to N3447 is situated
just 1.5' NE of center. It was highly suspected at 300x but could not be
confirmed with certainty.
PGC 32713
10 53 50.3 +16 51 02
18": very faint, very small, round, 10" diameter. Not difficult with averted
although this small galaxy has a redshift z = .086 or roughly 1.3 billion
light years! This galaxy is the brightest in Abell 1126 and is located 7.8'
NE of N3447. A neat right triangle of mag 12/13 stars are 2'-3' SSE. At
300x, one of the stars in the triangle is a very close (~1") double.
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Arp galaxies are always fun and you never know what peculiarities will be
visible. NGC 4211 = Arp 106 is a double system with a companion attached to
a spiral arm and a long tidal tail exiting the system.
N4211 = Arp 106
12 15 35.8 +28 10 39
V = 14.1; Size 1.2x0.8; SB = 13.9; PA = 105d
18": faint, very small, round, 25" diameter. This is a double, interacting
system (Arp 106) with a small, faint companion 0.55' SE. A mag 12.4 star
lies 2.8' NE. Third of three with N4196 and N4185 20' NW and 35' NW,
respectively.
N4211A = Arp 106
12 15 37.3 +28 10 11
V = 15.3; Size 1.4x0.3; SB = 14.2
18": this is an interacting companion to N4211 (Arp 106), situated just 33"
SSE of center. At 300x, this galaxy was extremely faint and small (0.2'
diameter) and just resolved from N4211. The DSS shows a faint tidal tail
heading south.
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Clouds started rolling in just before midnight (logged 35 objects), ending a
fairly brief but enjoyable evening.
Steve