SPACE.com -- Lunar Eclipse Tuesday Night to Dim Moon

What Youll See: Line and shading shows the extent of coverage expected at various times during the evening, as Earths partial shadow crosses the Moon from the upper left to the upper right.

The orientation of the Earth, Moon and Sun during a lunar eclipse, which can only occur at Full Moon.


	Lunar Eclipse Tuesday Night to Dim Moon By Diana Jong Staff Writer posted: 07:00 am ET 18 November 2002

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Hours after skywatchers are treated to the Leonid meteor shower of the century, they can head outside again to observe another celestial show. On the evening of Nov. 19, the full Moon will dip into Earth's shadow, creating a penumbral lunar eclipse.

Lunar eclipses, like solar eclipses, are created by geometrical alignments of the Sun, Earth and Moon. The Sun casts two areas of shadow behind Earth. The umbra is a region of total shadow. It is flanked by two cone-shaped areas of semi-darkness called the penumbra.

Penumbral eclipses can occur because the Moons orbit is tilted 5 degrees compared to Earth's plane of movement around the Sun. When the Moon crosses into the umbra, partial or total lunar eclipses occur. Penumbral eclipses occur, naturally, when the Moon enters the penumbra. Lunar eclipses happen only when the Moon is full.

The first contact between Moon and shadow will be at 6:32 p.m. EST (23:32 UT). Along the West Coast of the United States, the eclipse begins during daylight and before the Moon rises. Viewers there will see a portion of the event whats visible after the sun goes down and the Moon comes up.

The eclipse will peak at 8:47 p.m. EST and will end at 11:01 p.m. EST. Various portions of the event will be visible to half of the world, including the Americas, Europe, Africa and Central Asia.

The Moon will venture into Earth's penumbral shadow farther than it has all year, but the event will not be as obvious as total and partial eclipses.

"If one looks very carefully, one can see during this eclipse that the top edge of the Moon will be a little bit darker than the bottom edge," says Fred Espenak, an astrophysicist at NASA's Goddard Space Flight Center. "Almost like there's a cloud covering part of the Moon."

The best view is reserved for those who will see the eclipse as the Moon is rising or setting, around 6 p.m. and 6 a.m. local times, according to Espenak.

"It's actually easier to detect a penumbral eclipse under those conditions because there's not so much of a contrast between the Moon's disk and the sky background," he said. "In a black sky, the Moon is so bright that it is very difficult to tell that one edge is a bit fainter than the other."

A telescope, however, may help observers detect the eclipse more easily, Espenak said.

There will be two total lunar eclipses next year, in May and November. They both will be visible from the Americas, Europe and Africa. The most recent total lunar eclipse visible from the United States was in July 2001 and was enjoyed by Hawaiians.

And unlike solar eclipses, there's no danger to the eye during a lunar eclipse, Espenak said.