Your guide to the total solar eclipse

The partial eclipse
A partial eclipse of varying extent will be widely visible across all but the southernmost part of Africa, as well as all of Europe, the Middle East and western sections of Asia. The closer you are to the totality path, the larger the eclipse.

Across much of central and eastern Europe, the eclipse will be a midmorning to early-afternoon event, with the moon appearing to cover at least half of the sun’s diameter at maximum.  For parts of Greece, Turkey, Bulgaria, Romania and Ukraine, more than 80 percent coverage will result in an eerie “counterfeit twilight” effect at the peak of the eclipse.

Full prediction details for many cities are available from NASA.

In addition, NASA astronomer Fred Espenak has a Web site dedicated to the eclipse, which contains maps, tables and additional prediction details.

Be careful!
Once again it bears repeating: To gaze at the partially eclipsed sun without proper eye protection is dangerous. 

By far, the safest way to view a solar eclipse is to construct a “pinhole camera.”  A pinhole or small opening is used to form an image of the sun on a screen placed about 3 feet (1 meter) behind the opening.  Binoculars or a small telescope mounted on a tripod can also be used to project a magnified image of the sun onto a white card.  Just be sure not to look through the binoculars or telescope when they are pointed toward the sun!

A variation on the pinhole theme is the “pinhole mirror.”  Cover a pocket-mirror with a piece of paper that has a quarter-inch (6mm) hole punched in it.  Open a sun-facing window and place the covered mirror on the sunlit sill so it reflects a disk of light onto the far wall inside.  The disk of light is an image of the sun’s face.  The farther away from the wall, the better: The image will be only 1 inch (2.5 centimeters) across for every 9 feet (2.75 meters) from the mirror. Of course, don’t let anyone look at the sun in the mirror.

Acceptable filters for unaided visual solar observations include aluminized Mylar.  Some astronomy dealers carry Mylar filter material specially designed for solar observing. Also acceptable is shade 14 arc-welder’s glass, available for just a few dollars at welding supply shops.

Unacceptable filters include sunglasses, color film negatives, black-and-white film that contains no silver, photographic neutral-density filters, and polarizing filters.  Although these materials have very low visible-light transmittance levels, they transmit an unacceptably high level of near-infrared radiation that can cause a thermal retinal burn.  The fact that the sun appears dim, or that you feel no discomfort when looking at the sun through the filter, is no guarantee that your eyes are safe.

Remember: Only if you are in the path of totality, and only during those moments when the sun is totally eclipsed, is it safe to gaze directly at the sun.

Future eclipses
On Sept. 22, a spectacular annular solar eclipse will be visible soon after sunrise from parts of the South American nations of Guyana, Suriname, French Guiana and Brazil. Since the moon will be too small to completely cover the sun, the sun will appear as a fiery ring of light. 

In 2007, there will be two partial solar eclipses, on March 19 (mostly over northern Asia) and Sept. 11 (over the southern half of South America). 

The next total solar eclipse will occur on August 1, 2008, and will be visible from northernmost Canada, Russia, western Mongolia and parts of central China.

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