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How to get a good look at heavenly Venus

* 2 June 2004 *

How to get a good look at heavenly Venus

Scientists and amateur astronomers are eagerly awaiting the transit of Venus on 8 June, but what exactly is it - and what's all the fuss about?

Weather permitting, Britain will be able to view the celestial spectacle of the planet Venus crossing in front of the sun during the morning of 8 June.

It's a rare occurrence - the last one was in the 19th century - and as it won't be generally visible in the UK again this century, the transit of Venus is building up to be one of the most publicised events since the last - and less rare - total solar eclipse, in 1999.

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

What is it? The transit of Venus is a rare event in which 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 actually fully move onto the solar disc. The event ends around noon, (12h 04m 05s).

Can everyone see it, and what will it look like? You'll need to use strong, safe filters (ie with No. 14 grade glass, as used for welding) or those approved for solar viewing - never use sunglasses. The small and 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 (see below).

WARNING: Never look into the sun without using a proper filter, as it can lead to permanent eye damage.

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 easily see the progress of the black disk of Venus on its transit across the white solar disk - on the paper. This also works with binoculars mounted on a tripod. Make sure that neither you nor anyone else can accidentally look through the eyepiece while the telescope is aimed at the Sun.

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 event.

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 neither will be at all visible from the UK).

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.

Is the Earth in any danger from this event? Absolutely NOT! Just sit back and enjoy this harmless and impressive celestial show (using appropriate protection from the sunlight, of course - see above).

Where can I find out more? The BAA (British Astronomical Association) has created an informative website:

* Notes for editors *

The Astronomy Centre is part of the Department of Physics and Astronomy in the School of Science and Technology at the University of Sussex. For more information, see 

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