1993 ALMANAC FOR STAR GAZERS

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Nineteen ninety-three offers extraordinary sights for watchers of the heavens. The United States gets treated to a rare trio of total lunar eclipses—each one likely to provide strange effects due to the Earth-shrouding haze produced by Mt. Pinatubo's 1991 eruption in the Philippines. Prospects range from good to excellent for observing the major annual meteor-showers as well as numerous pairings and groupings of Moon, planets, and stars. This year brings a partial eclipse of the Sun to some parts of the country and some of the best planet appearances for years to come to the whole world.

ECLIPSES

A lunar eclipse is when the Sun, Earth, and Moon are in a straight line and the Earth's shadow falls on the Moon. In a total eclipse, the Moon passes completely into the Earth's umbra, or shadow, so that the Sun can't be seen from the Moon at all. In a partial eclipse, only part of the Earth's umbra falls across the Moon, and the Sun is partially visible from some places on the Moon. The third type, a penumbra eclipse, is when only the Earth's penumbra (partial shadow) shades the Moon and one's view of the Sun is only partially blocked by the Earth. (This type of eclipse is particularly difficult to detect from the Earth.)

A solar eclipse, on the other hand, is when the Moon passes between the Earth and Sun. In a total eclipse, the Moon covers the Sun completely and for a few minutes, the sky turns dark. In a partial eclipse, the Moon covers only a portion of the Sun; and in an annular (ring-shaped) eclipse, the Moon is too far from the Earth to cover the Sun completely so that a ring of light surrounds the Moon.

Considering the fact that the Earth can go without a total lunar eclipse for several years (even a decade in some locations), it is remarkable that the entire country will get a chance to see at least one of three total lunar-eclipses in a 12-month period, and possibly even a partial solar eclipse. Here's what you should look for:

December 9, 1992. This first eclipse begins just after nightfall, low in the eastern sky along the East Coast. The farther west you go, the farther advanced the eclipse will be by the time the Moon comes up, around sunset. West Coast watchers will catch only the last part of the Moon sliding out of the Earth's central shadow. During the eclipse, the Moon will pass through the northern part of the umbra—the part most likely to be most darkened by the sulfuric-acid haze of Mt. Pinatubo. Normally, our atmosphere bends a lot of light around the Earth, resulting in a cheerful orange or pink color for the totally eclipsed Moon. However, this may be one of those rare times when Earth's shadow is so dark that the Moon seems to disappear completely.

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