Observers across North and South America, eastern Europe and Africa will be treated to a spectacular total lunar eclipse the evening of Thursday, January 20 -- expected to be the best total eclipse visible in the Americas since September 1996.
The eclipse, less than two days past the moon's closest approach to Earth for the month, officially begins at 9:02 p.m., Eastern Standard Time (6:02 Pacific Time) as the moon enters the outer fringe of Earth's shadow, called the penumbra.
Observers may not notice anything at first because, at the moon's distance, the penumbra is about 10,000 miles (16,000 kilometers) in diameter and rather attenuated. A half-hour or so into the eclipse, however, most people will notice that moon appears "shaded."
At 10:01 p.m. EST, the eclipse begins in earnest as the eastern lunar limb enters the darker core of Earth's shadow, called the umbra, which is about 5,500 miles (9,000 kilometers) across at the moon's distance. At this time, the partial phase of the eclipse gets underway.
Observers will be able to see the curved shape of Earth's shadow gradually close over the moon. Aristotle and other ancient observers cited the round shape of Earth's shadow cast on the moon during a lunar eclipse as one of the earliest proofs that Earth is spherical.
Maximum eclipse, or totality, occurs at 11:04 p.m. EST and lasts almost an hour and 20 minutes. This is when the most eerie aspect of a lunar eclipse occurs. The moon can still be seen, but it is illuminated by sunlight refracting (bending) through Earth's atmosphere. Blue light is bent the least, but red light is bent the most, just as it is at sunset and sunrise.
This gives the moon a dull, coppery hue. Brighter stars can often be seen shining next to the moon's limb, especially in binoculars, making the whole scene look like a huge, mottled ruby set among tiny diamond chips. Just how red the moon will appear depends largely on the clarity of the atmosphere.
For the first time since Mount Pinatubo's eruption in 1991, the atmosphere is finally clear of volcanically lofted aerosols. This eclipse, therefore, may be fairly bright during totality.
Totality ends at 12:22 a.m. EST, and by 1:25 a.m. the moon exits the umbra altogether. Finally, at 2:24 a.m., the moon edges out of the penumbra, bringing an end to the eclipse.
You won't need a telescope nor will you need to find particularly dark skies, unless you want to see as many faint stars during totality as possible. Perhaps one of the best ways to view a total lunar eclipse is with binoculars. A telescope will give you a close-up view of the umbra falling across the craters, but with their wide views and sharp optics, binoculars give you a striking perspective on the entire drama of totality.
The final total lunar eclipse of the year occurs July 16, 2000.
Unfortunately, except for observers in Hawaii and western Alaska, the total phase of this eclipse occurs after moonset for most observes in the Americas. This makes viewing the January 20 eclipse all the more important.
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