New Delhi: Giving thousands of sky gazers a rare visual treat, planet Venus today (June 8, 2004) started its transit across the disc of the Sun even as experts warned against watching the event through the naked eye.

"Star gazers have gathered here to watch the once in a lifetime event. Venus appears as a tiny black dot passing across the face of the Sun," Director, Nehru Planetarium, Dr N Rathnasree, told.

The brightest planet, after about 122 years, started crossing the disc of the Sun at 10:43 hrs (IST) and will take about six hours to cross it, she said.

Rathnasree, however, warned against looking at the Sun through the naked eye as it may lead to eye problems.

"Looking directly at the Sun could lead to vision problems," she said, adding the safest method is to see it through a projection.

The event, similar to a solar eclipse, is visible from all over India. Since the Venus does not cover the face of the Sun, it appears as a tiny dot moving from the Sun's south-eastern edge to south western, president of an amateur astronomers NGO 'SPACE', Amitabh Pandey, said.

The transit could also be seen from other Asian nations, Africa and Europe. Eastern parts of the US and Australia could see the end of the event, he said.