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Lunar Guidance

February 13, 2011

The bright gibbous Moon can guide you to one of the biggest star patterns in the sky tonight: the Winter Circle. The Moon is near the star the marks the circle's hub, bright orange Betelgeuse.

As night falls this evening, look directly below the Moon for the Dog Star Sirius, the brightest star in the night sky. If the Winter Circle were the face of a clock, Sirius would mark the six o'clock position. As you circle clockwise around the Moon, you'll come to Procyon, the little dog; Pollux and Castor, the twins of Gemini; Capella, in Auriga, the charioteer; Aldebaran, the eye of Taurus, the bull; and finally Rigel, at the heel of Orion, the hunter.

Except for Pollux and Castor, all of the stars on the circle's rim helped guide Apollo astronauts on their trips to the Moon.

The coordinates of about 45 stars were loaded in the guidance computers of both the command ships and the lunar landers. The astronauts found these stars through a telescope, and used the star's positions to plot their location in space. They didn't use all of the stars at once, though -- only a few at each observation. But the long list gave them plenty of choices based on what was in view at the time. The observations served as a backup to the tracking network on Earth.

Look for the Winter Circle forming a giant ring around the Moon throughout the evening -- a circle of stars that helped guide astronauts to the Moon four decades ago.


Script by Damond Benningfield, Copyright 2010


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