Mostly clear skies forecast for Venus transit

1.00pm

LONDON - Europe, Africa and the Middle East are the best vantage points to see the first transit of Venus across the sun in more than a century on Tuesday, scientists said.

Mostly clear skies are forecast in many parts of the three regions, but people were urged to be careful if they watch the rare event when it begins at 0519 GMT (1719 NZT) because it could cause blindness. Views will be restricted from Asia and the Americas.

In New Zealand, the only chance to see the transit is in the Far North, briefly at sunset.

Unlike a solar eclipse by the moon that is over in two or three minutes, Venus' transit -- which last occurred in 1882 -- will go on for six hours.

The planet will appear as an intense black dot on the solar disc.

Most of the sun will be visible as Venus crosses to the right from the bottom left side of the solar disc. Venus will be 43 million km from earth.

"Venus will be about 1/30 the size of the diameter of the sun, but it will be much darker and more intense than sunspots," said Dr Robert Walsh, of the University of Central Lancashire's Centre for Astrophysics in northern England.

Scientists recommend some form of indirect projection as the safest way to observe the phenomenon.

"Never ever look directly at the sun with the naked eye or any sort of optical equipment -- telescope, binoculars or even digital camera," said Walsh.

"Even if you glance at the sun for a short period of time you can damage your eye and lose some of your sight," he said.

Internet sites will be covering the transit and observatories around the world have organised viewings.

"Mainly Western Europe could see some high cloud that might prevent people from seeing it," said a spokesman for Britain's Meteorological Office. "The rest of Europe shouldn't be too bad. It should be fine."

German astronomer Johannes Kepler first predicted a transit of Venus in 1627 but he died before he could witness one. English astronomer Jeremiah Horrocks first observed it in 1639.

The transit occurs four times in every 243 years. There are two December transits, eight years apart, and then 121.5 years later there are two June transits, also eight years apart. After another 105.5 years the cycle begins again.

The next transit will occur in 2012 when it will be visible from parts of Asia and the Pacific but not Europe.

- REUTERS

For updates and pictures see: Venus Transit 2004

University of Lancashire

Nasa