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The Sky This Week, 2011 March 8 - 15

A waxing Moon, Mercury returns, and don't forget to "Spring Forward"!
STS_ISS_110307_04small.jpg

Space Shuttle "Discovery" and the International Space Station
passing through the stars of the "Big Dipper".

A 15-second time-exposure made from Alexandria, Virginia,
2011 March 7, 23:59 UT.


The Moon waxes in the evening sky this week, coursing a high path through the departing winter constellations. First Quarter occurs on the 12th at 6:45 pm Eastern Standard Time. Look for the Moon about seven degrees north of the bright star Aldebaran on the evening of the 11th. The famous Pleiades star cluster will be about 10 degrees west of the fattened crescent on that same evening. On the 14th Luna lies just over a degree south of the third-magnitude star Delta Geminorum. Can you see the star despite the Moon’s proximity?

This is the week when we once again go through the annual ritual of setting our clocks one hour ahead to Daylight Time. Officially this happens on the 13th at 2:00 am local time, but best practice dictates that most of us advance our clocks before turning in on the evening of the 12th. The use of Daylight Time has been a controversial subject ever since it was first widely introduced during World War I. Definition and enforcement of Daylight Time rules were, with a few exceptions, the responsibility of individual states until the Uniform Standard Time Act became law in the 1960’s. Since that time two changes have been made in the dates for commencement and cessation of Daylight Time, with the current rules defined by the Energy Policy Act of 2005. We now observe Daylight Time from the second Sunday in March until the first Sunday in November. This is almost a full month longer than the duration of Standard Time, which makes me wonder which system should now indeed be "standard". Fortunately, the agency responsible for promulgating the law and its rules is the Department of Transportation, so disgruntled citizens still have a place to call and voice their views.

Daylight time to me means that I’ll lose an hour of sleep, then everything that occurs in the evening sky takes place an hour later than what I’ve been used to. Most of the time I don’t like this, but this week I’ll make an exception. The planet Mercury is making his best evening showing for the year, and daylight Time means I won’t have to rush home to catch him as he dances along the twilight horizon. He spends the week closing in on bright Jupiter, starting about 10 degrees below the giant planet as the week begins and passing just 2 degrees north of Old Jove on the evening of the 15th. The best time to look for him is about 45 minutes after sunset, when he will be high enough above the horizon to see without the aid of Jupiter. Mercury will leave the giant planet in his wake as he heads toward greatest elongation on the 23rd. By the time Mercury drops back into the twilight glare, Jupiter will be gone as well.

The disadvantage to Daylight Time is that, after Saturday evening, you’ll have to wait an extra hour to see Saturn at his best. As the week opens the ringed planet rises shortly before 8:00 pm EST. This places him at a good viewing altitude by around 10:30. Once we’re on Daylight Time everything shifts an hour later, meaning you’ll either have to stay up later to catch him on the rise or get up in the wee hours to view him at culmination. Nevertheless, the view of Saturn through a small telescope is worth almost any inconvenience if you can take advantage of steady air. The planet and his majestic rings are worth losing a little sleep over.

Bright Venus still greets us in the pre-dawn sky. She rises about an hour and a half before the Sun in the southeastern sky, and remains visible through the gathering twilight until Old Sol is clearing the horizon. Venus will remain a fixture in the morning twilight sky until well into the summer months, finally fading into the solar glare by early August.

USNO Master Clock Time
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