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Moon to nibble at sun for Christmas eclipse

It won't be much of a show, experts say, but they think it's a neat Christmas gift, anyway.

By DAVID BALLINGRUD

© St. Petersburg Times, published December 23, 2000


For the second time in 46 years, there will be a partial eclipse of the sun on Christmas morning.

In the Tampa Bay area it will begin at 11:03 a.m., reach its maximum at 12:31 p.m. and be finished at 2 p.m.

A solar eclipse occurs when the moon passes between the sun and Earth, and its shadow sweeps across part of the Earth's surface. People in the shadow experience an eclipse.

People are not supposed to look directly at a solar eclipse, but in this case most probably won't notice it anyway.

"If you didn't know about it, you wouldn't know it took place," said St. Petersburg Junior College math and astronomy professor Daryl Schrader. "It will not noticeably dim the sun."

Still, "it's neat that we are having one on Christmas Day," he said, "It's kind of a little Christmas gift. But it would be a lot more fun if it were a total eclipse."

Agreed, said NASA astrophysicist Fred Espenak, who maintains a Web site (www.MrEclipse.com) specializing in eclipse photography.

In Florida, he said, "only about 20 percent to 26 percent of the sun's surface will be eclipsed. You really need 90 percent or more before the human eye notices anything significant."

The event will be visible throughout nearly all the inhabited parts of North America, as well as from most of Mexico and the Caribbean.

The most dramatic sight -- the biggest crescent-shaped bite into the sun's surface -- will take place in the upper Midwest and eastern Canada, according to Espenak.

Even in those places, however, the light will dim only slightly.

Looking at the sun is uncomfortable, and so people seldom do. But during an eclipse, it can be tempting. The result can be "eclipse blindness," a serious eye injury that can cause temporary or permanent blurred vision or blind spots.

Sunglasses won't help.

During the last total solar eclipse visible from the eastern United States, on March 7, 1970, nearly 150 people suffered some eye damage, according to Astronomy magazine.

Half of them never regained their full eyesight.

Astronomy has bound solar eclipse glasses into its January edition. Other good filters include commercially available Mylar filters and metal-on-glass filters, the magazine says, or a No.14 arc welder's glass. These materials sharply reduce the amount of visible light and remove all the sun's more dangerous ultraviolet and infrared radiation.

For an indirect but safe view of the eclipse, try constructing a simple pinhole camera.You need two pieces of cardboard and some aluminum foil. Cut a modest-sized hole in one piece of cardboard and tape the aluminum foil over it. Then use a straight pin to poke a small hole in the foil.

To view the eclipse, have the sun's light pass through the pinhole onto the second piece of cardboard.

The next Dec. 25 solar eclipse, by the way, occurs in 2307.

Mark your calendar.

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