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Tips on viewing the partial solar eclipse 21 August 2017

Eye Health UK the charity behind, the National Eye Health Week campaign, is warning about the dangers of looking directly at the sun during the partial solar eclipse on 21 August.

A partial solar eclipse will be visible in Britain just before sunset on Monday when the moon covers 10 per cent of the sun’s diameter and two per cent of its area.

The phenomenon will continue for around 40 minutes and by visible across areas of England, Wales, Scotland and Northern Ireland from around 7.35pm. Visit http://www.timeanddate.com/eclipse/in/uk for accurate eclipse viewing times across the UK.

Even though the weather forecast is for cloudy skies people must ensure they take proper precautions when viewing the phenomenon.

Looking directly at the sun, even for a moment[1], can lead to irreversible damage to the eye, solar retinopathy – a photochemical reaction that damages and destroys the light receptor cells that enable us to see. The symptoms of solar retinopathy, which may not become apparent for hours or even days after exposure to the Sun, include a black spot appearing in the centre of your vision, light sensitivity and reduced visual acuity. There is no specific cure for the condition, which in severe cases can lead to permanent sight loss.

David Cartwright, Chairman of the Charity Eye Health UK, explains: “Anyone looking directly at the sun during the eclipse risks causing permanent damage to their eyesight so we are urging people to enjoy this rare cosmic event by viewing it indirectly. Children are particularly susceptible to damage because the lens of a child’s eye allows 70 per cent more light to reach the retina than in an adult[2].”

The fact that the sun or the sky may seem ‘dull’ during the eclipse does not mean it is safe to look at with the naked eye, sunglasses, smoked glass or optical instruments such as binoculars, telescopes or cameras.

The only completely safe way to view the eclipse is indirectly. You can do this using a simple homemade pinhole card.

Just take a piece of stiff card and pierce it with a pin. Stand with your back to the sun, and hold the card up. Then, carefully adjust the angle of the card until an image of the Sun is projected. You can project the image onto the ground, a wall or a second piece of card.

Alternatively, you could use an ordinary kitchen colander to project an image of the sun. This is great fun for kids as you can project multiple images at the same time!

It is possible to purchase special eclipse viewing solar filters, although it is vital to ensure that any filter you use is specifically made for solar observation, carries a CE Mark and that it is not scratched or damaged. Make sure you hold the special filter firmly over both eyes BEFORE looking up at the Sun, and don’t remove it until AFTER looking away. The sun should look quite dim and the sky should be completely black - if this is not the case then DO NOT USE THE FILTER.

If you are in any doubt about eye safety you can watch the eclipse on one of the many live webcasts being broadcast from countries along the path of the eclipse.

 

[1] British Ophthalmological Surveillance Unit. In 39% of patients presenting to hospital ophthalmologists after the 1999 eclipse, the time spent looking at the eclipse was reported to be less than 60 seconds

[2] The Vision Centre, Los Angles Children’s Hospital

 

 

Published : 21 August 2017