Opus Observes: Jupiter and Friends
- From: brian@xxxxxxxxxxx (Brian Tung)
- Date: Sat, 18 Jun 2005 08:20:51 +0000 (UTC)
9:00 p.m. 17 June 2005 PDT (2005-06-18-0400 UT)
After about a week of the marine layer coming in just around dusk (and
thereby frustrating my attempts to get any nighttime observing done), I
finally got some clear skies. In spades, as it turned out.
I set up the scope around 8:00 to try to get a decent view of Jupiter.
It took a little while longer than I expected for Opus to cool down, and
I didn't really get any decent observing of Jupiter until 9:00. (This
was at 210x with the 6 mm Radian.) At that point, the GRS was still
three hours away from crossing central meridian, so it hadn't even crept
out onto the daytime side yet.
The seeing was about 2 arcseconds, and moderately fast, but still slow
enough that I could see it moving from south to north. (Down to up, in
other words.) In contrast to previous observing sessions, in which there
were few festoons, on average, there were no fewer than four festoons in
evidence tonight, with the first and third (counting from preceding to
following limb) more prominent than the second and fourth. They made
quite a sight. In the SEB, just to the following side of the central
meridian, there was what I thought was a notch on the southern edge of
the belt. Perhaps it was an oval? The seeing was not sufficiently good
to tell in the small scope.
One other thing I noted was that the belts were more similar in color
than I had ever seen them. During my first Jupiter apparition in
1997-98, the belts were quite different in color, with the NEB being
much redder (or more orangey, perhaps) than the greyish SEB. Now, the
difference seems much smaller than before.
I also wanted to do some DSO hunting. I switched to the 24 mm Panoptic
(52x) and tried warming up with some easy globulars, M4 and M80, but M4
proved to be very hard to see, as it was still rising. I deferred those
for a moment.
The sky looked to be promising (for a light-polluted location, anyway).
Albireo beckoned; it was the first nighttime target I ever pointed the
C5+ at. Even now, seven years on, it's still a great sight. With a
background of dimmer stars, the 68-degree panorama has a
three-dimensional appearance to it, the yellow-blue pair standing out
from the dim crowd.
With Aquila now up out of the horizon haze (this was about 11:00 local
time), I pointed the scope at M11. What a beautiful sight this
incredibly rich open cluster is. Under light-polluted skies, it's hard
to tell this cluster from a very bright globular. Maybe the sharp angle
near the eighth-magnitude star is a giveaway. The angle seems to me to
be more than 90 degrees, closer to 100 or 110, although perhaps that's
an illusion, resulting from the fact that that star isn't quite at the
corner but grab's the eye's attention. What do others think about that?
My first new target was NGC 6755, in Aquila. This smallish open cluster
can be found by drawing a line from theta Aquilae, through delta
Aquilae, and extending it about a third of the way past. It's listed as
being a quarter of a degree across. I found a handful of tenth- and
eleventh-magnitude stars; I couldn't tell if there was anything deeper
(although I strongly suspect there is). It's probably just not an
appealing target in suburbia.
Better were two clusters in Vulpecula. Before heading to those, I
checked out M27, the Dumbbell Nebula. Amazingly bright, even under these
skies. Stands out like a sore thumb, and even without a nebula filter,
it shows some texture to it. It lies off 14 Vulpeculae, the center star
of a distinctive W or M pattern.
Off the western star of the W, 12 Vulpeculae, is the first of the two
Vulpecula open clusters I observed, NGC 6830. This is a small open
cluster, just 6 arcminutes across--a tenth of a degree. The Vulpecula
W/M pattern has a couple of wide doubles in it, and NGC 6830 is embedded
in a smaller, dimmer equilateral triangle of wide double stars. It's a
pleasing asterism in its own right. The cluster lies on the northern
edge of the triangle, a bit off center. It consists of a few
tenth-magnitude stars, but unlike NGC 6755, there is a distinct sense of
some dimmer stars lying just outside individual detection, registering
only as a granular haze. Not a bad little cluster, and one I'll make a
note of looking at when I next get under dark skies.
Following along the same line from M27 to NGC 6830 is NGC 6823, which
lies an equal distance away. I've actually observed this one before,
about a year ago, on a suggestion from Bill Ferris. It's also pretty
small, listed as only an arcminute wider than NGC 6830. It sits at the
apex of a wide angle made of four stars; interestingly, just a fraction
of a degree away is a smaller angle of three stars, exactly parallel to
the first, so that the pair make a kind of chevron. Another provocative
asterism. This cluster has a bit less depth than NGC 6830, but there is
still a sense of some dim member stars behind the first several tenth-
and eleventh-magnitude stars.
By this time, the sky had darkened significantly--dark enough *and*
steady enough that the Double Double, epsilon-1,2 Lyrae, was visible to
the unaided eye as a tight pairing, just over three arcminutes apart.
Many times in my backyard, I can't distinguish them, only because the
sky is too bright for their light to be made out quite directly. But
tonight, it was no problem. I estimated the zenith limiting magnitude to
be over 5.0, almost unheard of in Santa Monica. At 52x, each pair of the
DD was just barely split, with the southern pair (the more equal one)
more easily so.
M4 and M80 were now quite easy to see, and M4's central north-south bar
and granular appearance were fairly straightforwardly discernible. I was
encouraged to seek out another globular further westward, NGC 5897, but
unfortunately, that cluster was only 17 degrees from the waxing gibbous
Moon. I found the exact spot where the globular should be, but try as I
might I couldn't make it out at all.
Last but not least, I pointed the scope at Jupiter again, now setting in
the west. The GRS was now sitting at central meridian, and even at only
52x, the GRS hollow could be made out. I couldn't see the GRS itself at
that low power, though.
Brian Tung <brian@xxxxxxx>
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt
.
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