for National Geographic News
Just in time for the Halloween season, the moon Wednesday will treat us to its most famous trick: changing from bright white to reddish as it passes deeply through Earth's shadow.
This will be the last total lunar eclipse until March 3, 2007, and the last eclipse that will be easily viewed throughout the entire continental U.S. until February 21, 2008.
"For North America, this particular eclipse I refer to as the prime-time eclipse," said Fred Espenak, an eclipse expert at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "It's ideally suited for casual observing."
The partial and total phases of the eclipse will be visible in the evening sky throughout most of the Americas. In the western third of the continental U.S., the moon will already be very faintly eclipsed when it rises. In Alaska the moon will already be fully eclipsed at moonrise.
Europe and Africa also get a view of this eclipse, but at a less convenient time: the early hours of Thursday morning.
A total eclipse of the moon occurs when the full moon passes through the inner portion of Earth's shadow, known as the umbra. The umbra blocks all direct sunlight from reaching the moon. The penumbra, or outer shadow, blocks some, but not all of the sun's light.
Not until the night of February 20, 2008, will the entire population of the continental U.S. be able to step outside and catch an eyeful of an eclipse before crawling into bed for the night.
In the U.S. the March 3, 2007, event will be visible from the eastern half of the nation while the August 28, 2007, eclipse is best viewed from the West during the wee hours of the morning, Espenak said.
Wednesday's eclipse gets underway in earnest at 9:14 p.m. eastern time, when the moon's eastern edge begins moving through the umbra, causing it to darken to a reddish hue.
"The change is dramatic," writes Alan MacRobert, a senior editor with Sky and Telescope magazine in an article on the event. "A dark dent forms in the moon's eastern side, and as the minutes tick by, the dent becomes a big, curved bite."
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