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October 2004 Feature: Total Eclipse of the Moon


The evening of October 27 presents a total eclipse of the Full Hunter's Moon. The Moon first enters into the Earth's dark shadow (umbra) at 9:14 p.m. Eastern Daylight Time, at which time the partial phase of the eclipse begins. One hour and nine minutes later, at 10:23 p.m., the Moon becomes completely immersed in shadow, undergoing a total eclipse. Mid eclipse -- the eclipse's darkest hour -- comes to pass at 11:04 p.m.

Totality lasts for one hour and twenty-two minutes. The Moon begins its exit out of the Earth's shadow at 11:45 p.m., with a partial eclipse lingering onward for one hour and nine minutes. When the Moon completely leaves the Earth's shadow by 12:54 a.m. (Oct. 28), the very slightly waning Moon will be basking in sunshine once again.

If the Moon orbited the Earth on the same plane that our Earth orbits the Sun, then we'd have a total eclipse at every full Moon. As it is, the Moon's orbital plane is inclined at about five degrees to Earth's orbital plane. (Oftentimes, the Earth's orbital plane is called the ecliptic.) For half of the month, the Moon in its orbit travels north of the ecliptic, and for the other half of the month, the moon travels south of the ecliptic. Twice a month, the Moon intersects the ecliptic at points called nodes.

Generally, eclipses don't happen at full Moon. That's because the full Moon usually eludes the Earth's shadow by orbiting above it or below it. When a full moon passes appreciatively close to its node, however, a lunar eclipse is not only possible -- but inevitable.

So if it's clear on the evening of October 27, be sure to witness this sky watching spectacle. The next total eclipse of the Moon won't be coming round again till the year 2007!

Click here for a map of this eclipse, courtesy of Eclipse Predictions by Fred Espenak, NASA/GSFC

by Bruce McClure

Another October Feature: Saros Eclipse Cycle

More eclipse stories:

November 8-9, 2003 Total Lunar Eclipse
May 15-16, 2003 Total Lunar Eclipse