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The Sky This Week, 2010 August 31 - September 7

Meandering along the Milky Way, Planets at dusk & dawn.
MoonVen_100814_01small.jpg jupc8_100814_0605_01small.jpg

Spica, the Moon, Mars, Venus, & Saturn
Imaged over Hay Harbor, Fishers Island, NY,
2010 August 13, 20:45 EDT
Canon PowerShot S2IS, 10 sec. @f/5, ISO 100

Jupiter, with Io & Europa
Imaged from Fishers Island, NY
on 2010 August 14, 06:05 UT

The Moon wanes in the pre-dawn sky this week, with Last Quarter falling on September 1st at 1:22 pm Eastern Daylight Time. Luna begins the week in the company of the Pleiades star cluster on the mornings of the 31st and the 1st. She then wends her way as a waning crescent through the rising stars of the Great Winter Circle. On the morning of the 3rd she passes just south of the star cluster Messier 35 in Gemini. You should be able to spot the cluster in binoculars, but you should also have no trouble finding the familiar outline of Orion directly below the Moon as twilight begins to gather. From an ocean-facing horizon you should be able to see all the stars of the Great Winter Circle before twilight begins to wash out the view.

As the calendar steers us toward the last few weeks of astronomical summer the sky finds itself in a period of transition from summer’s bright stars to the relatively dim constellations of autumn. We are approaching the time of the year when the length of daylight is decreasing at its most rapid rate, so summer’s constellations seem to linger for awhile in the evening sky. Take advantage of this if you haven’t had a chance to go someplace well away from city lights to explore the billowy star clouds of the summer Milky Way. With evening astronomical twilight now ending at a decent hour of around 9:00 pm you have several hours of darkness to investigate this amorphous river of light and still turn in at a civilized time. Binoculars and my 3.1-inch rich-field telescope are my favorite tools for delving into the cosmic lagoons and backwaters of the galaxy, and from a dark location it is truly amazing at the number of stars and nebulae one can see with such modest optical aid. As the midnight hour approaches the southern sky becomes bereft of bright stars and Milky Way clouds, but if you turn your attention toward the northeast another arm of the Galaxy is swinging into view. After the star clouds of Sagittarius and the Summer Triangle have faded to the west, the area between Cassiopeia and Perseus is filled with yet more treasures for your enjoyment.

The evening twilight sky is still dominated by the bright glow of Venus, but the dazzling planet doesn’t stay visible past the end of evening twilight. Even though she reached her greatest elongation east of the Sun two weeks ago, her position on the Ecliptic keeps her low for northern hemisphere observers. This week she passes by the bright star Spica on the evenings of the 31st and 1st, gliding just over a degree south of the star. A few nights later the much dimmer planet Mars passes some 2 degrees north of Spica as he attempts to keep pace with his more dazzling planetary consort.

Late night skywatchers have been treated to the golden glow of Jupiter in the east as the giant planet rises a couple of hours after sunset. Old Jove is now just a few weeks from opposition, so he now rises on average about four minutes earlier each night. By the end of the week he will crest the horizon at around 8:00 pm, so those of us with early bedtimes can enjoy a good telescopic view of his streaked surface by 10:00 pm. He’s still missing his normally prominent South Equatorial Belt of dark clouds, so seasoned Jupiter observers are watching him like a hawk to see if there are any signs of the belt’s resurgence.

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