China will see the longest total solar eclipse in 500 years on July 22, a scientist said Saturday.

The prime time of the total eclipse was expected to begin from 9 a.m. to 9:38 a.m. (Beijing Time), said Wang Sichao, a research fellow with the Nanjing-based Purple Mountain Observatory under the Chinese Academy of Sciences.

People watch the newly-installed equatorial sundial, measuring 1.5 meters in diameters, donated by the National Observatory to mark the spot for observation of the forthcoming 2009 total solar eclipse on the Yangtze Valley, believed to be the longest one visible in the century that is to betide on July 22, in Haining, east China's Zhejiang Province

"The total eclipse will last up to six minutes, or the longest one that can be seen in China in almost 500 years from 1814 to 2309," Wang said.

He said viewers in parts of 11 provinces in China's southwestern, central-southern and eastern areas, such as Tibet, Hunan and Jiangsu, will be able to witness the total solar eclipse, while in most parts of Shanghai, viewers can see the spectacular phenomenon.

Photo taken on July 11, 2009 shows the sketch maps illustrating the whole process of the full solar eclipse during a popular science exhibition on the introduction to the forthcoming 2009 Full Solar Eclipse at the Shanghai Science & Technology Museum in Shanghai, east China. The upcoming full solar eclipse, predicted to betide on July 22 and believed to be the longest of its kind in 500 years, will be visible in most parts of the Shanghai Municipality.

For viewers in other provinces, including Beijing, they can observe a partial eclipse, he said.

A solar eclipse occurs when the moon is caught between the sun and the earth while each of them moves along their fixed orbits.

In a total solar eclipse, the sun, the moon and the earth are directly aligned as the sun swings into the cone of shadow cast by the moon.

The upcoming full solar eclipse, predicted to betide on July 22 and believed to be the longest of its kind in 500 years, will be visible in most parts of the Shanghai Municipality.

Wang said the next total solar eclipse that can be seen in China will fall on March 20, 2034.

"But it can only be seen remote provinces, such as Tibet and Qinghai. It cannot not be compare