In what will look like a partial eclipse, Venus will cross the bottom half of the sun on Tuesday in a six-hour spectacle. The crossing will be similar to the transit of Mercury last year but more dramatic: because Venus is larger and closer to Earth it will block out more of the sun, covering approximately 1/30th of the star's face. Because the spectacle will take place when the sun is high in the sky it should be visible across Hong Kong, provided there is no cloud cover, although a Hong Kong Observatory spokesman said: 'The best places to observe the transit will be those with an unobstructed view to the west, such as Pokfulam, Stanley, Lamma Island, Cheung Chau and Tai O.' Staring directly at the sun, even through sunglasses, can permanently damage one's sight; the transit should be watched through a projected image only. It can be safely observed using a telescope by standing with your back to the sun and projecting the image onto a piece of white card. Hundreds of people are expected to witness the transit at the Hong Kong Space Museum, where it will be shown on a large indoor projector screen. It can also be watched live online by logging on to www.lcsd.gov.hk/CE/Museum/Space . The observatory spokesman added: 'Because of the strong sunlight, people must neither look directly at the sun with the naked eye nor through a telescope. They should also avoid observing the transit for a prolonged period.'