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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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