Your guide to the total solar eclipse

By Joe Rao

Skywatching columnist

updated 11:10 p.m. ET March 24, 2006

Amateur and professional astronomers from around the world will congregate in parts of Brazil, Africa and western Asia to view a total eclipse of the sun on Wednesday. Without a doubt, a total eclipse of the sun is one of the most spectacular natural sights that one can witness.

Only during totality can one observe the pearly white solar corona, as well as the ruddy chromosphere and prominences — sights that are normally hidden from our view by the brilliant light of the sun itself. In addition, darkness similar to 20 or 30 minutes after sundown suddenly falls over the surrounding landscape, allowing the brighter stars and planets to appear while strange and exotic colors rim the horizon.

Contrary to popular belief, a total eclipse of the sun is not a rare or unusual spectacle.

In fact, over the past 25 years there have been no fewer than 16 total solar eclipses, an average of one roughly every 18 months.  The regions from which the spectacular sight of a totally eclipsed sun can be seen, however, are strictly confined to a narrow track; the path that the dark central shadow of the moon (called the “umbra”) traces out over the Earth’s surface.  That track may run for thousands of miles, yet may average less than a hundred miles in width.

While the dark lunar shadow might sweep over Earth twice over a span of just three years, for a specific geographical location, the odds of lying directly in the path of that shadow is very small. 

So if you intend to wait for this, the greatest of celestial road shows to come to your hometown, your wait is likely to be (on average) about 400 years.  That is why many dedicated eclipse watchers — sometimes referred to as “umbraphiles” — will literally chase total solar eclipses around the globe.  All for the privilege of “basking in the moon’s shadow” for a few precious minutes.

The last time skywatchers had an opportunity to see the sun in total eclipse was last April, when the moon’s umbra briefly touched Earth over the South Pacific Ocean for an unusual “hybrid” eclipse. Besides being accessible only to shipboard observers, the maximum length of totality lasted only about 42 seconds.

In contrast, this week's eclipse will be far more accessible and totality will last much longer: just over 4 minutes in the Libyan Desert.

Only six other times over the past quarter century have there been total eclipses that have lasted as long as this; this will be the longest total solar eclipse that occurs between June 2001 and July 2009.

Region of visibility
The path of totality for this eclipse begins over easternmost Brazil, where the coastal city of Natal and adjacent communities will be treated to the spectacle of a total solar eclipse shortly after the sun has come over the horizon. But this is a very humid climate and is prone to low clouds and coastal fog, which could very well eclipse the eclipse. Nonetheless, many South Americans will likely congregate here hoping against hope for a break in the overcast to afford them a glimpse of the sun’s corona.

Quickly moving offshore and in a northeastward direction, the dark umbral shadow of the moon will then take 36 minutes to sweep over the open waters of the North Atlantic. 

It finally makes landfall again in western Africa, moving inland over Ghana and plunging its capital city of Accra into a late-morning darkness for three minutes and four seconds.  Continuing on a northeasterly trajectory, the totality path slices through Togo and Benin, and into northwestern Nigeria.  The cities of Gusau and Katsina, fortuitously positioned near the center line of the eclipse track, will each experience just over three minutes and 50 seconds of total eclipse.  But typically, early spring is the rainy season for all of these regions, so the odds are not very good for getting a good view of the sun.

The totality path will then cut across central Niger, northern Chad and central and eastern Libya (just barely missing the city of Tobruk). The greatest eclipse, where totality will last for four minutes and 6.7 seconds, occurs along the border of Chad and Libya.  Weather prospects in these areas improve dramatically, as this is basically a desert regime. But while there’ll probably be a paucity of clouds, local haze and dust might be a problem.

Passing over the Mediterranean Sea, directly between Crete and Cyprus, the eclipse track sweeps through central Turkey, where the towns of Kayseri and Sivas will experience more than two minutes of totality.  Unfortunately, this is also near an active storm track, which usually brings a 40 to 70 percent chance of clouds.

After passing over the Black Sea, totality will strike the northwest corner of Georgia, then move across Kazakhstan before leaving Earth at sunset along Mongolia’s northern border.

MORE FROM TECHNOLOGY & MONEY

Technology & Money Section Front

Dad lost his job, so this family lives on the road Living on the road full-time: Is it right for you? Do you need a mini money makeover?   Insider shares shopping secrets   Ford unveils inflatable seat belts   Experts offer financial advice Recession over? Readers don't believe it   How to deal with rising credit card rates   U.K. gets tough on distracted drivers   College dorms get an upgrade Technology & Money Section Front   Add Technology & Money headlines to your news reader: