U.S. TO SEE CHRISTMAS ECLIPSE
WILLIAMSTOWN, Mass., Dec. 11, 2000—A partial solar eclipse will be visible from the entire continental U.S. on Christmas Day, Monday, Dec. 25.
Jay M. Pasachoff of Williams College said "it is fascinating to see any solar eclipse, even a partial one when the moon covers the sun in the middle of the day. It is important, though, to observe it safely. Reports of eye damage are very rare, and if everyone observes the eclipse properly, the damage level will be zero."
The eclipse will peak at in the early morning on the west coast, with 14 percent of the sun covered in Los Angeles and over 35 percent covered in Seattle at between 8:30 and 9 a.m. At about 11 a.m., the sun will reach Dallas, with 35 percent of the sun covered. Over 50 percent of the sun will be covered in the early afternoon in Boston, New York, Philadelphia, Chicago, Pittsburgh, Detroit, and Washington, D.C.
Pasachoff is director of the Hopkins Observatory at Williams College, Williamstown, Massachusetts. He is also chair of the Working Group on Eclipses of the International Astronomical Union.
"A solar eclipse occurs when the moon comes between the sun and the earth," explained Pasachoff. "On December 25, the tip of the moon's shadow will remain off in space, and never hit the Earth's surface. Thus, we will see the moon only partially covering the sun. It will look as though a bite has been taken out of the sun’s surface."
Though the sun will be partly covered, it is still not safe to look at directly. A pinhole camera is the safest way to observe the partial eclipse. To make one, simply punch a hole 1/4-inch across in a piece of cardboard, and hold the cardboard up to the sun so that the shadow of the cardboard falls onto a piece of white paper. Look down at the paper, and not up through the hole in the cardboard. In the middle of the white paper, you will see the image of the sun, which will look like a circle with a bite out of it. Often, without making your own pinhole camera, you will find such pinhole images on the ground or on a wall under a tree, since the interstices between the leaves or branches act as natural pinholes.
"If you want to look up toward the sun, you must have a special filter," explained Pasachoff. "Ordinary sunglasses are not safe. The filter must block out all but about one part in a million of the light that hits it, and must do so all across the spectrum, even in the infrared. Neutral density filters sold for cameras are not safe either. Special solar filters that block out enough light are commercially available. They usually are made of deposits of a film of metals on a plastic or glass backing."
Pasachoff's "Peterson Field Guide to the Stars and Planets" (Houghton Mifflin Co.), widely available in bookstores, describes how to observe and how to photograph eclipses and all types of other sky phenomena. An updated edition has just been released. See www.williams.edu/astronomy/fieldguide.
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