Image by n0ll via Flickr

Image by luc.viatour via Flickr

About once each year, there is a solar eclipse somewhere in the world. However very few people ever get the chance to see one. Often they occur at night, the area they are visible from is usually small, and the weather must be clear of clouds. On the 22nd of July 2009, there will be a opportunity to see a total solar eclipse in central China.

What is a solar eclipse?

Image via Wikipedia

As the moon orbits around the Earth, occasionally it's path crosses directly between the Sun and the earth. Due to slight wobbles in the Earth's and moon's orbits, most of the time the moon passes either above or below the sun. But just occasionally there is a direct alignment. The moon, passing in front of the sun, obscures the sun from view turning day into night in what is called a Solar Eclipse. Even then, there is often a small discrepancy and the Eclipse is only partial. Only in a small area of the Earth, can a total eclipse be seen. In a total eclipse, the sun is completely obscured from view.

Why are total eclipses important?

When the moon passes in front of the sun, it blocks out the light that normally floods our view. For just a few short minutes, we are able to see things around the sun that we cannot normal look at. Flairs of gas streaming out from the sun suddenly become visible. For this reason many scientists travel round the world chasing after Eclipses.

How to view the eclipse

Warning: Do not look at the sun directly. Not even during the eclipse. Looking at the sun can seriously damage your eyes and even cause blindness. Even looking for just a few seconds can cause permanent damage. Only during the short period of totality, when the moon completely covers the sun, can the sight be viewed and even then great care must be taken. Even a near complete eclipsed sun can damage your eyes.

Warning: Do no use a camera or telescope to view the sun directly. The lens will increase the potential damage caused by the sun to your eyes. Additionally you may cause damage to your camera.

To view the sun safely, there are a variety of methods. The safest of these is to use a lens and a piece of card. The lens projects the suns image onto the card and you can look at the card safely and watch as the moon passes in front.

An alternative to a lens can be to use a simple pinhole viewer. To make this you just need two pieces of card. Make a hole in one card using a pin or nail. Stand with your back to the sun. Place the card with the pin hole several inches in front of the other card and adjust the position so that the light passing through the pin hole falls on the second card. An image of the sun should be visible on the second card which can be viewed safely during the eclipse.

Image by unfoldedorigami via Flickr

If you are able to, you can purchase special glasses or lenses for your camera which can allow safe viewing of the sun. These lenses look completely black under normal light but when looking at the sun they allow just enough light through to let you see the events as the happen. These do however come with a warning. Before using special glasses to view the sun, you must ensure that there is no damage to the lens The smallest of scratches to the protective surface may render the glasses useless and dangerous to use.

Where can the Eclipse be seen?

On the 22nd of July 2009. The first part of China to be able to view the solar eclipse will be northern Yunnan. It will then pass across southern and central Sichuan, central Hubei and Southern Anhui. The last areas to see the solar eclipse will be southern Jiangsu, Shanghai and Northern Zhejiang. The map below shows you the areas affected.

Even if you are not in these cities, a partial eclipse will be visible over all of China to varying degrees. Again, great care must be taken when viewing these.

Image by NASA