The UK will experience a partial solar eclipse on the morning of 4th January 2011, leading the Department of Health's Chief Medical Officer to issue advice on "safe viewing" of this stellar event.
As the eclipse will occur between 8.00 and 9.30 in the morning, if the weather is clear then it will be easily seen by millions of children on their way back to school after the Christmas break. During a previous eclipse in 2005 a young boy suffered damage to his central vision after looking directly at the sun, so it is important that everyone, children and adults, is aware of the dangers and the right precautions to take.
Anyone who wants to experience the eclipse must do so either by indirect means or by using special eye protection. Just because you experience no pain looking at the eclipse does not mean that your eyes have not been damaged, so follow this advice to be certain of a safe viewing experience.
Direct viewing
•Sunglasses are NOT safe. They do not block the harmful radiation that causes eye damage.
•To directly view the sun, you need to use properly designed and certified solar filters. These will be identified as such, and should have the CE mark and a statement that it conforms to EC Directive 89/686/EEC. Alternatively a welder's glass rated 14 or higher can be used.
•Even with the correct filters in place children could still be at risk if the fitting is designed for an adult's face. These should only be used by children with fully trained adult supervision.
Indirect viewing
This is the safest way to see the eclipse. A simple home-made "pin-hole" camera can be constructed to view the eclipse. You will need two pieces of thin but stiff sheets of white cardboard.
•Make a very small, clean hole in one piece (with a sharp pin).
•Stand with your back to the sun.
•Hold up the sheet with the hole so that it is exposed to the sun.
•Place the second sheet below the first. An inverted image of the sun should be cast on the second sheet.
•To make the image brighter, move the screen closer to the pinhole.
Do not make the pinhole wide or you will only have a shaft of sunlight rather than an image of the crescent sun. Remember, this instrument is used with your back to the sun. The sunlight passes over your shoulder, through the pinhole and forms an image on the cardboard screen, beneath it.
DO NOT look through the pinhole at the sun.
Remember under no circumstances should you look directly at the sun.
