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The Sky This Week, 2010 September 14 -21

Looking over the Moon, Jupiter at opposition

The Moon
Imaged 2009 NOV 22, 23:45 UT
with a 50mm f/10 "Galileoscope"
and a Canon PowerShot A95

The Moon brightens the evening sky this week as she wends her way through the southern constellations of the Zodiac. First Quarter occurs on the 15th at 1:50 am Eastern Daylight Time. She starts the week off to the east of the bright star Antares in the constellation of Scorpius, then drifts over the "Teapot" asterism of Sagittarius before entering the nearly empty sky of the autumnal constellations. By the end of the week she will approach Jupiter as the latter approaches opposition.

It has been said many times that the Moon is "looked over, then overlooked" by amateur astronomers. Typically Luna is the first thing that owners of new telescopes focus their attention on, but after a few sessions spanning a few lunations they feel that they’ve seen all there is to see on the Moon’s desolate face and move on to other things. Those of us who enjoy the hunt for "faint fuzzies" or the intricate structure of the larger bright nebulae and star clusters often regard the Moon as the bane of our pursuit. However, our only natural satellite is also the one object that can be seen easily from virtually any location, no matter how blighted our sky is by local light pollution and smog. It doesn’t require much of a telescope to easily see Luna’s countless craters and other geological features, but the larger the telescope the more detail you’ll see. The Moon is the only object in the sky where we can spot features that come close to a scale that we humans can appreciate. The smallest crater pits visible in a typical amateur telescope are about a kilometer across, a distance most of us can walk in less than 10 minutes. In celebration of our closest neighbor in space, the evening of the 18th has been designated as the first annual International Observe the Moon Night (InOMN). This event is sponsored by "Astronomers Without Borders" in collaboration with NASA, whose Lunar Reconnaissance Orbiter (LRO) and Lunar CRater Observation and Sensing Satellite (LCROSS) projects met with great success last year. Here’s a chance to amaze your friends and neighbors with a glimpse of Luna through your telescope. Information on InOMN, including charts depicting Luna’s appearance on the 18th, may be found on the official website.

Moving outward from the relatively nearby frontier of the Moon, Earth’s next-closest neighbors in space are still vying for attention in the evening twilight sky. You should have no trouble spotting Venus shortly after sunset in the southwest. The dazzling planet reaches her greatest brilliancy in the evening sky this week, and maintains that brilliance for the next couple of weeks. She stands out well in the deepening twilight, and on exceptionally clear days may be glimpsed with the unaided eye some 40 degrees east of the Sun if you block Old Sol’s direct glare from your view.

Much harder to pick out is Mars, which tags along with Venus about six degrees to the north and west. The red planet is about 100 times fainter than his brilliant rival, so you’ll probably need binoculars to pick him out of the horizon glow half an hour or so after sunset.

As Venus settles toward the horizon, another bright object becomes prominent in the eastern sky. Giant Jupiter reaches opposition on the morning of the 21st, at which time he will be closer to us than at any time since 1951. His location among the faint stars of Pisces makes him stand out even more prominently, and many people have commented on the planet’s brightness to me lately. After gazing at the Moon, turn your telescope toward Old Jove. You’ll be rewarded for your effort!

Early risers can catch a glimpse of fleet Mercury just before sunrise in the eastern sky. The planet reaches greatest elongation on the 19th, and should be an easy object to spot in the gathering twilight glow about half an hour before the Sun comes up.

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