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OR: Venus, Jupiter, the Moon



 
 
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Old May 29th 04, 02:52 AM
Axel
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Default OR: Venus, Jupiter, the Moon

Date: May 26, 2004
Location: Grady Park in uptown Houston TX
Telescopes: 90 mm apo refractor, 8" f/6 Newtonian reflector
Seeing: 7/10 to 8/10

A quick summary of our observations:

This night we had the common combination of poor transparency and good
seeing. Polaris was often barely visible! At about 8:45 PM CDT Randy
and I set up in the grassy area in the middle of the walking loop,
positioning ourselves so that some trees obscured the bright lights at
the nearby tennis courts. The tall Marathon Oil Tower blocked a large
part of the western sky, including where Saturn was, but Venus was
visible to the northwest about 10-15° above the horizon.


Venus
Even to my astigmatic naked eyes, Venus was obviously not circular.
Since the planet was close to setting, I skipped most of the
preliminary business and just plopped the Dob on the ground, quickly
collimated, and inserted a Nagler 12mm for 102x. The view was
stunning. By far the thinnest crescent phase I've seen it at. It was
amazing how far the cusps of the crescent wrapped around the planet,
more than halfway around it appeared to us. No doubt this is because
of internal reflections within the clouds. The thin lit portion was
boiling quite a bit since Venus was so low. The color of the part
directly facing the sun seemed somewhat yellower to me than the rest
of the crescent, but this could have been chromatic aberration in the
eyepiece.


Jupiter
Now that Venus was done, we could take our time. Set up the tables,
EQ platform, eyepieces. Crack open a cold beer. We spent a while on
Jupiter, maybe an hour. The planet was high and the seeing good, so
there were moments of great clarity. A thin white roiling stream of
turbulence was evident throughout both the NEB and SEB. The GRS was
well on its way to the eastern limb, but the color change within it
was still visible. A strong hint of an Equatorial Band was visible
over a significant range of longitude.

We noticed a prominent barge in the NEB, portruding into the EZ, on
the western side of the disc. As this barge rotated towards the
center, two very interesting loop festoons became visible emanating
from the barge in opposite directions, touching the equator, then
looping back to the NEB. Both were about the same size (I reckon
large enough to contain most of the Earth), with the eastern one a
shade darker. However, even that one wasn't what I'd call
"prominent". Over the last few weeks I'd been hearing of prominent
festoons on Jupiter, but all I can conclude is that they must be on
the other side of the planet!

Other miscellaneous details: The STZ was *much* thinner than its
counterpart the NTZ. Randy pointed out a white oval in the STB,
perhaps 20° of longitude west of the GRS. At 250x in the Newt, I
noticed a tiny white circular notch on the northern edge of the NEB,
just east of the barge described above. Also, the NEB was getting
wider to the west, and at the end of the session (after the Moon)
nearly equaled the SEB in width.

One thing I noticed is that the phase of Jupiter was not very
discernable this night. The eastern limb seemed a bit softer than the
western, but actually it should be the other way around, unless I'm
mixing up my mental map of the orbits. Anyway, apparently we've swung
around far enough in our orbit that it's difficult to make out the
dark side of Jupiter. The phase was certainly obvious a couple months
ago.


The Moon
Randy had brought his Rukl Atlas of the Moon, so we spent a very
enjoyable hour on our nearest neighbor. One inconvenience of that
outstanding atlas is that the map key numbers are in red, so they
literally disappear under red light. Which drug were they on when
they made that design decision? Of course, red light and dark
adaptation aren't really an issue when observing the Moon. But it's
still not comfortable at night to stare at a white page with white
light reflecting off it.

We began with the Vallis Alpes and tried to glimpse the rille running
along its floor, but only saw a hint of it at the southwestern end. I
tried powers well beyond 700x, but the rille eluded me. Maybe the
angle of illumination wasn't favorable. However, the nearby Montes
Alpes were casting impressively long and jagged shadows onto Mare
Imbrium. The shadow from the isolated Mons Piton was truly gigantic.
According to Rukl, this mountain is about 7400' tall, sticking
straight out of the mare. Not much like that here on Earth!

The terminator was just at the rim of Plato, so it wasn't possible to
try for its craterlets. So we moved on to explore Mare Nectaris to
the southeast. The bright small crater Rosse sits in the mare, with a
white streak extending out to both the southwest and northeast. Large
Fracastorius with its missing northern wall (probably melted by the
mare lava flows) was nearby. Piccolomini to the south had a very
interesting central mountain massif complex, with strange sheer ridges
on two sides. I bet it's a really impressive view standing next to
that massif. Other interesting craters in the region were Beaumont
(interrupted wall) and Bohnenberger (rumpled floor).

A bit northeast is Mare Fecunditatis, which was quite washed out by
sunlight this night. The pair of craters Messier and Messier A lie in
the mare, with two very prominent ejecta rays streaking to the west
from Messier A. We looked for Rima Messier but couldn't find it.
After giving up, we moved to the much larger Rima Hyginus and Rima
Ariadaeus to the northwest. The lower angle of illumination here
proved much easier on the eyes and gave a more detailed view. These
two rilles are very long (220 km each) and broken in many places. The
nearby highlands are quite rough. The crater Boscovich to the north
of the rilles has a thin rille bisecting it.


End
Clouds had been rolling across the Moon for a little while now, so we
took one last (unproductive) look at Jupiter and called it a night.

Cheers,
Ritesh
 




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