Scientists and amateur astronomers are eagerly awaiting the rare celestial spectacle of the planet Venus crossing in front of the sun during the morning of 8 June.

To help explain the importance of this 'transit of Venus', Dr Peter Schroeder of the Astronomy Centre has compiled a star-gazing beginners' guide, addressing the most commonly asked questions:

What is it? The planet Venus passes between the Earth and the Sun by crossing the solar disk. The first recorded transit viewing was in 1639.

When is it? At 06h 19m 54s BST on the morning of Tuesday 8 June. It will take about 20 minutes for Venus to fully move onto the solar disc. The event ends around noon (12h 04m 05s).

Why is it so special? A transit of Venus is a very rare event. Usually, whenever Venus passes between us and the Sun, it misses the solar disk. The last transit of Venus was in 1882, so no living person has seen such an occurrence.

Is this an important event for scientists? Venus transits caused great scientific interest in the 18th and 19th centuries, as they were used in an attempt to find the distance scale of the solar system. Since then, however, much more accurate methods have emerged, for example, measuring the delay time of radar reflections.

Can everyone see it, and what will it look like? You'll need to use strong, safe filters - never use sunglasses. The small, black-as-ink disk of Venus will be visible even to the unaided eye, as it will cover 1/32th of the apparent diameter of the solar disc. There are many supervised viewing events planned around the country and viewing goggles are available from the British Astronomical Association for £1.

Is there a safe method to observe this event with a small telescope? Yes. Project the image of the Sun onto a white sheet of paper or cardboard, using a low-power eyepiece. You can then see the progress of the black disk of Venus on its transit across the white solar disk - on paper. This also works with binoculars mounted on a tripod.

When is the next transit of Venus? They come in pairs, about eight years apart. The next one will therefore be in 2012, but only part of it will be visible from the UK. For the next pair of transits, however, you will have to wait until 2117 (but that transit won't be at all visible from the UK).