Total Lunar Eclipse

2011 Total Lunar EclipseIf the sky is clear, observers in the Southwest can see the first stages of a total lunar eclipse on the morning of Saturday, December 10. Varying portions of the event will also be visible across much of the globe.

The eclipse officially begins at 03:33 PST when the Moon’s orbit begins taking the Moon into the Earth’s penumbra, or outer shadow. During this phase of the eclipse, the Moon will be very slightly shaded, but the effect will be too subtle for most people to notice.

The eclipse’s partial phase begins at 04:45 PST, when the Moon begins entering the Earth’s umbra, or inner shadow. At first, a small, black dent will appear on the Moon’s limb. The dent will then slowly grow and advance across the Moon’s face.

Totality begins at 06:06 PST when the Moon completely enters the umbra. For the next 51 minutes, a portion of the sunlight from the Earth’s day side will be refracted, or bent, around the Earth by the atmosphere and directed into the umbra. The light will give the normally white Moon a dull copper color.

Unfortunately, the brightening of the sky and the setting of the Moon will prevent observers in the Southwest from seeing the entire event. Generally, the further you move to the west-northwest, the more of the eclipse you will see. For example, for observers in New Mexico, totality begins around moonset. On California’s Central Coast, however, more of the event will be visible with the Moon setting around the end of totality.

To see Saturday’s eclipse, all you’ll need are a clear sky, the naked eye, and a vantage point with an unobstructed view of the western horizon. Selecting a viewing site with a good view of the west is of particular importance due to the Moon’s very low elevation during the hour before sunrise.

For a better view of the Moon’s disappearing act, use binoculars or a small telescope. However, for the best view, use tripod mounted binoculars.

by Brian Webb

Here are a couple good reads about the Dec. 10, 2011 Total Lunar Eclipse & NASA.

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