A partial eclipse of the sun will take place over the Washington area at midday today, but weather forecasters and astronomers say the solar spectacle probably will be obscured here by overcast skies.

"As far as watching [the partial eclipse], you may pretty well forget it," said National Weather Service forecaster Harold Hess, noting that thick clouds and rain are predicted for today.

While the sun will be only partly eclipsed behind the moon here, a total solar eclipse will sweep across five Western states and parts of Canada more than 700 miles northwest of Washington today. According to astronomers, it will be the last total eclipse of the sun to traverse North America in this century. The next such eclipse to touch the continental United States will be in the year 2017.

The eclipse will reach its maximum point of 68 percent over the Washington area at 8 minutes and 37 seconds past noon, according to U.S. Naval Observatory astronomer Thomas VanFlandern. The moon will begin to eclipse the sun at 10:52 a.m. here and will complete its passage across the sun's face at 1:25 p.m. At its maximum eclipse here, the sun -- if visible -- would resemble a large crescent with a black notch carved out by the moon, VanFlandern said.

Astronomers and ophthalmologists have warned that observers of the eclipse -- where it is visible -- should avoid gazing directly at the sun to avoid possible serious damage to the retinas of their eyes. Sunglasses, smoked glass and welder's goggles are also described as providing insufficient protection against eye injuries from the sun's infrared rays.

There is considerable disagreement about whether an eclipse may be viewed safely through several layers of exposed and developed black-and-white film. Some astronomers recommend this method and describe it as safe, but several ophthalmological groups have described such photographic film as insufficient protection.

Astronomers and opthalmologists have suggested several safe ways of viewing an eclipse without looking toward the sun. One is to aim a telescope at the sun, without looking into it, and then focus the sun's image through the telescope onto a white board located about six inches behind the instrument. Another technique is to make a small hole in a white sheet of heavy poster board and use this as a lens to focus the sun's image upon a second white sheet. A similar device may be constructed from a cardboard box by fastening white paper inside one end of the box, making a pinhole in a patch of aluminum foil attached to the opposite end to serve as a lense, and cutting a hole in the bottom of the box from which to view the sun's image.

Never look at the sun directly through the pinhole, scientists say. CAPTION: Illustration; Viewing the Solar Eclipse

1. Select a box to use as a projector. The longer the box, the larger the image will be.

2. Tape a white piece of paper to the inside of the box.

3. Opposite the paper, punch a small hole through the box, about 1/16" in diameter.

4. With your back to the sun, align the box until the sun's rays pass through the hole and shine onto the paper.

5. Hope for a clear day. (Word Illegible) -- The Washington Post.