Onlin [e] Guid [e]

A rare total solar eclipse will occur this afternoon -- when the moon will pass directly between the earth and the sun -- but it will be visible as a partial eclipse in India. The eclipse will begin in Arctic Canada and sweep across Greenland, western Siberia, Mongolia and central China. In India, the visual treat will start at 4:03 pm in Delhi and last for about two hours with maximum impact at 5:02 pm. In rest of the country, the partial eclipse will be visible a few minutes later.

Nearly 15 lakh pilgrims are expected to take a holy dip in Brahm Sarovar at Kurekshetra where security has been tightened due to recent serial blasts in Bangalore and Ahmedabad. Viewers all across the globe can see the eclipse as it happens on NASA TV and by logging on to www.nasa.gov. The US space agency has made arrangements to telecast live images of the rare celestial event.

"The partial eclipse will be seen in the north-eastern region, starting from about 4 pm," said Rathnasree, Director at the Nehru Planetarium. The maximum obscuration of the sun will occur at Sibsagar in Assam.

The biggest and last phase of the eclipse will be visible from most parts of the country, except Nagaland and Mizoram, where it ends after sunset, she said. Solar eclipses do not take place every month because of the tilt of moon's orbit around the earth which is elliptical, like the earth's orbit around the sun. Therefore, the moon and the sun do not always appear to be precisely the same size in the sky.

The next solar eclipse -- a partial one -- will occur on January 26, 2009 but the phenomenon will be marginally visible from eastern and southern India.

But on Friday, the southern parts of India will see between 20 to 40 per cent of the sun's diameter while the northern parts of the country will see between 40 to 70 per cent of the sun's diameter. Experts say viewing the eclipse with naked eyes could be dangerous.

Major planetariums have made arrangements to show the eclipse to the enthusiasts and amateur astronomers through telescope using mylar solar filter in a projection system. Solar eclipses have typically inspire a combination of dread, fascination and awe for thousands of years. In recent times, they have also become popular events for tourists across the world.

In total eclipses, the sun vanishes, the stars come out in daytime and temperatures drop briefly.