Totality, when the entire moon is inside the umbra, should begin at 10:23 p.m. ET and last an hour and 22 minutes until 11:45 pm ET. According to Espenak, this duration of totality is on the "long side of average."
By contrast, totality for the last widely visible eclipse in the U.S., on November 9, 2003, lasted only 24 minutes. The maximum totality duration possible is an hour and 47 minutes, which last occurred July 16, 2000.
After totality, a partial eclipse ensues as the moon slips out of the umbra. Excluding the faint, penumbral phases, the entire event lasts 3 hours and 40 minutes, with the partial eclipse ending at 12:5.4. am ET on Thursday.
Deep Eclipse
During a total lunar eclipse, the moon does not go completely dark. While the Earth stands between the sun and moon during totality, a certain amount of light is bent, or refracted, by Earth's atmosphere and illuminates the moon.
The atmosphere scatters most of the short wavelengths of light—blue, green, and yellow—out of the refracted light. Therefore, primarily the orange and red rays reach the moon, giving it the orange-reddish glow, according to scientists.
The more dust in the air from volcanic eruptions, forest fires, or pollution, the more scattering of the refracted light takes place and the less light reaches the moon.
According to Espenak, the atmosphere is currently relatively free of dust. Even though volcanic activity has recently occurred at Mount St. Helens in Washington State, "most of the activity so far is water vapor, which won't have much impact on the lunar eclipse or changing the coloration of it," he said.
However, Earth's umbral shadow is darker in the center than on the edge. On Wednesday night the moon will pass just north of the shadow's center, causing the southern portion to be darker than the northern edge.
Eclipse Observing
Unlike solar eclipses, a lunar eclipse is safe to look at with the naked eye—no special filters or glasses are required to block out harmful rays of light. Astronomers suggest looking at the moon through binoculars and telescopes to enhance the colors.
The only thing that is critical for viewing a lunar eclipse is a view unobstructed by tall buildings, trees, or mountains.
According to Espenak, North American observers will be treated to the fall and winter constellations during the eclipse. The moon will be in southern Aires, Pegasus will be to the west, and Taurus and Orion will be to the east.
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