The longest solar eclipse expected to occur in the 21st century became visible at sunrise Wednesday local time in Taregna, a village in eastern India, and moved across a 155-mile-wide ribbon of Asia including areas of Nepal, Bangladesh, China and part of the Pacific Ocean,.
The total eclipse started when the moon completely blocked out the sun in the village, which scientists said was the best place to view the spectacular event, at 6:24 a.m. local time.
In Varanasi, India, a town on the Ganges River, clear skies allowed the curious to get a perfect view of the event, but over much of the region there were heavy clouds, disappointing millions who hoped to see the eclipse.
That could include eclipse enthusiasts from around the world who descended on the region to view the event by land, sea and air to catch a glimpse of the phenomenon, which lasted six minutes and 39 seconds in some areas.
Awed by the rare experience of watching the moon block the light of the sun, "eclipse chasers" go to the ends of the Earth, often paying thousands of dollars for the perfect view and the maximum duration of darkness.
"Most people who go on these tours, they've seen one or more eclipses. They become hooked on it," said Paul D. Maley, a NASA contractor leading an eclipse tour in Shanghai, China, for Houston-based Ring of Fire Expeditions, an astronomical tour organization.
A solar eclipse takes place when the moon passes between Earth and the sun. If the moon's inner shadow falls on Earth's surface at that moment, the sun's light is blocked by the moon. A total solar eclipse only happens about once every 18 months and is only visible from the path of the moon's inner shadow.
On a clear day, it also exposes the sun's corona (or halo-like outer atmosphere) that is usually invisible in daylight.
A week ago, Maley arrived in China with 40 armchair astronomers and, after days traveling from Shanghai to Tibet and back, the group planned to venture to a nearby city early Wednesday morning to watch the main event. From their viewing site, they expected to see five minutes and 26 seconds of totality, starting at 9:35 a.m. local time (9:35 p.m. ET tonight).
Maley has led eclipse tours since 1970 (across more than 22 countries) but said he has watched the numbers of eclipse chasers climb in recent years.
"Interest has been slowly getting larger, year by year," he said, adding the upswing started most clearly in the 1980s and 1990s as Americans and Europeans starting having more disposable income with which to travel.
In addition to his own group in Shanghai, he said his organization is leading two other similarly sized groups in the city and another one in the Gilbert Islands. While many of the participants are also scientists, he said, they span all kinds of occupations and all ages.
Jim Pritchett, a travel agent with Bartlesville, Okla.-based Spears Travel, said about half of the 39 people on his company's eclipse tour in China are veteran chasers. The average participant has been on seven or eight of its tours, he estimated.
Spears tours are especially attractive as they are led by Fred Espenak, a recently retired leading NASA scientist, widely known as "Mr. Eclipse."