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Mercury, Mar/Apr 2002 Table of Contents

Copyright 2001 by Fred Espenak (www.MrEclipse.com).

by Fred Espenak

A total eclipse of the Sun is arguably the most awesome sight in all of nature. Day is suddenly replaced with an eerie twilight and the Sun’s brilliant disk is blocked by the dark Moon. Only then is the Sun’s glorious corona revealed to all. This incredible spectacle is visible once every year or two when the Moon’s small dark umbral shadow races across our planet’s surface. The ensuing path of totality is typically about 150 kilometers wide but can stretch halfway around the globe. A partial eclipse may be seen from a large fraction of Earth, but only those lucky enough to be within the umbra’s track will witness the corona and totality.

The next total eclipse occurs on December 4, 2002. The path of the Moon’s shadow begins in the South Atlantic and sweeps across southern Africa. This is the beginning of the path, so the eclipse occurs in the early morning shortly after sunrise. Although December is the start of southern Africa’s rainy season, the weather prospects are reasonably good. Weather data suggest a 50% to 60% probability of clear skies during totality, especially along the path covering Zimbabwe, South Africa, and Mozambique. In this region, the total eclipse will last nearly a minute and a half with the Sun high in the eastern sky.

After leaving Africa, the Moon’s shadow will spend the next two-and-a-half hours racing across empty sea in the Indian Ocean. During the last two minutes of its trajectory, the eclipse shadow finally encounters southern Australia. The coastal town of Ceduna lies at the center of the path, where totality lasts a mere 33 seconds. Because of their brevity, short total eclipses offer exceptional opportunities to view the diamond ring and Baily’s beads. These sparkling jewels of sunlight are seen along the edge of the Moon’s disk just as totality begins and ends. They are caused by high mountains on the Moon, which break the Sun’s crescent into a string of brilliant beads that quickly vanish.

From the Australian section of the path, the eclipse takes place in the late afternoon just minutes before sunset. The totally eclipsed Sun stands 9° above the western horizon from Ceduna. Traveling with a ground speed of over 2,000 kilometers per hour, the shadow quickly moves northeast into the interior. Here a number of small towns lie within its path, including Wirraminna, Coondambo, and Purple Downs. Totality lasts 30 seconds in the region with the Sun 6° high. As it nears the end of its path, the Moon’s shadow brings totality to the Outback towns of Lyndhurst, Fort Grey, and Tickalara. Beyond this point, the shadow returns to space and the total eclipse ends.

As you might expect, Australia’s Outback offers the best weather prospects along the entire eclipse track. Satellite images and climate statistics indicate a 70% chance for clear sky during the eclipse. This optimistic probability must be tempered with the understanding that the Sun’s low altitude will magnify the effects of even a small amount of cloudiness. Eclipse chasers are likely to encounter late afternoon temperatures of over 40° C (100° F) in the Outback, with the possible threat of dusty whirlwinds. Ceduna offers relief from the high temperatures, but at a cost, because the coast is prone to strong, gusty winds and a 10% lower chance of clear sky.

The coast and interior portions of Australia’s eclipse path are readily accessible within a one- to two-day drive from Adelaide. Close weather monitoring, Internet access to the latest satellite cloud images, and mobility will increase your odds of locating the perfect spot to witness nature’s greatest spectacle.

Traveling halfway around the world for a 30 second eclipse might sound completely crazy, but the experience of totality is worth every second. A century ago, author and eclipse chaser Mabel Todd summed it up best when she wrote: "I doubt if the effect of witnessing a total eclipse ever quite passes away. The impression is singularly vivid and quieting for days, and can never be wholly lost. A startling nearness to the gigantic forces of nature and their inconceivable operation seems to have been established. Personalities and towns and cities, and hates and jealousies, and even mundane hopes, grow very small and very far away."