A total eclipse of the Moon will enchant skywatchers across almost all of North and South America during the evening of May 15-16, 2003. For observers in the eastern United States and Canada, southern Mexico, and all of Latin America, the eclipse will be visible from start to finish. For most North American observers west of an imaginary line that connects Green Bay, Wisconsin with Brownsville, Texas, the early stages of the eclipse will take place before the Moon rises, but the Moon will be visible during the most dramatic stages, when the eclipse reaches totality.

Lunar eclipses can only occur during the Full Moon when the Moon moves into Earth's shadow. This eclipse "officially" begins at 9:05 p.m. EDT (6:05 p.m. PDT) on May 15. That's when the Moon enters the outer portion of Earth's shadow, known as the penumbra. But most observers will not notice any changes on the Moon until about 9:45 p.m., when the eastern part of the Moon starts darkening. This early phase of the eclipse is known as a "penumbral eclipse."

The beauty of the eclipse will become readily apparent at 10:03 p.m. EDT, when the Moon enters the inner, darker part of Earth's shadow, the umbra. At this point, the Moon is in "partial eclipse," and a sliver of darkness on its eastern edge will be noticeable even to the most casual observer. The total eclipse, which begins when the Moon is fully inside the umbra, lasts from 11:14 p.m. EDT to 12:07 a.m. EDT on May 16. The Moon will again be in partial eclipse until it leaves the umbra at 1:17 a.m. EDT. The final penumbral phase of the eclipse ends when the Moon makes last contact with the penumbra at 2:15 a.m. EDT.

Even though Earth's shadow is larger than the Moon, the Moon is still visible when it is totally eclipsed, making it a grand spectacle easily noticeable to anyone with a clear sky and an unobstructed view. Earth's atmosphere filters out the Suns blue light by scattering it, and it refracts some of the Sun's red and yellow light, which strikes the Moon and often casts our neighboring world in an eerie, orangish glow.

"What's really neat about total lunar eclipses is that every one is different. The color of the Moon varies from eclipse to eclipse, depending on how much dust and other aerosols have been recently injected into the atmosphere by volcanic eruptions and forest fires," says Robert Naeye, editor of Mercury magazine, which is published by the Astronomical Society of the Pacific (ASP).

"Based on the depth of the eclipse and the fact that we haven't had any major volcanic eruptions recently, I'd guess the color will be orange to bright red," adds astronomer and eclipse authority Fred Espenak of NASA's Goddard Space Flight Center. Espenak maintains a website of eclipse information and photos at www.MrEclipse.com.

"Total lunar eclipses are fascinating to watch from start to finish as the Moon darkens and as its color changes almost minute by minute," says Naeye. "And a great thing about lunar eclipses is that they are totally safe to watch, and no optical aid is needed. Telescopes and binoculars can provide dramatic views of the eclipsed Moon, particularly by enhancing the colors. But the only things you need to enjoy the eclipse are a clear sky and an unobstructed view."

An unobstructed line of sight will be critical. At the time the eclipse starts for observers in the United States and Canada, the Moon will be very low in the southeastern sky, so people should find a location where their line of sight is not blocked by buildings, trees, or mountains. The Moon will rise higher as the eclipse unfolds, and will settle in the south-southwestern skies as the eclipse ends in eastern North America.

This eclipse will not be visible in Alaska or extreme northwestern Canada, and observers in Hawaii will only catch its final stages. Observers in Europe, the Middle East, and most of Africa will be able to watch the early stages of the eclipse, but the Moon will set before the eclipse has run its course.

"The May 15-16 lunar eclipse is the first really good lunar eclipse visible over North America since January 21, 2000," says noted astronomer and author David H. Levy, who is a member of the ASP's Board of Directors. The next total lunar eclipse visible in North America will occur on November 9, 2003.

Contact local amateur astronomy clubs, science museums, or planetariums to see if they are offering public viewing sessions for the eclipse. Publishable photos of past lunar eclipses, and diagrams of the May 15/16 eclipse, can be downloaded free of charge at this ASP website: www.astrosociety.org/news/lunarpr03.html. The photos and diagrams were provided by Fred Espenak and by Phil Harrington, author of the book "Eclipse! The What, Where, When, Why & How Guide to Watching Solar & Lunar Eclipses." Please credit Fred Espenak and Phil Harrington if you publish or broadcast their images.

For more information about this eclipse, including diagrams for time zones in North America and Europe, visit Fred Espenak's website at: http://sunearth.gsfc.nasa.gov/eclipse/extra/TLE2003May15.html. For information on how to photograph the eclipse, visit www.MrEclipse.com/LEphoto/LEphoto.html.

The nonprofit Astronomical Society of the Pacific was founded in 1889 in San Francisco and is still headquartered there today. The ASP has since grown into an international society. Its membership is spread over all 50 states and 70 countries and includes professional and amateur astronomers, science educators of all levels, and people in the general public. The ASP publishes the bimonthly Mercury magazine for its members, a technical journal for professional astronomers called Publications of the Astronomical Society of the Pacific, and an on-line teachers' newsletter. The ASP also coordinates Project ASTRO, a national astronomy education program. The Society produces a catalog and website of extensive astronomy-related products for educators and the public.