Sun spot: Mercury's silhouette will be seem moving across the Sun's disc on May 7.

Pray for good weather as a rare astronomical event will be visable in Hong Kong next week.

Mercury will pass over a portion of the Sun's disc on May 7. Its silhouette will be visible as it passes between the Sun and the Earth.

The process starts at 1.12pm and will last for more than five hours.

However, people must NOT look directly at the Sun with the naked eye or through a telescope or binoculars as this can cause blindness.

The safest method of watching the event is to project the Sun's image onto a piece of white paper or cardboard through a telescope or binoculars and view the projection.

The best places to observe the transit include Pok Fu Lam, Stanley, Lamma Island, Cheung Chau and Tai O where there is an unobstructed view to the west.

The last transit of Mercury was November 6, 1993, while the next one will not be until November 9, 2006. The phenomena only occurs 13 times a century.