SAFE SUN - VIEWING THE SOLAR ECLIPSE  

An eclipse occurs when the sun, earth and moon are in alignment, with the moon situated between the earth and the sun. When this happens the moon casts a shadow on the earth causing an eclipse.

The sun is 400 times the diameter of the moon but it is also 400 times further away from the earth. This causes the two objects to look as though they are the same size when seen from the earth.

In a solar eclipse, the moon moves between the earth and the sun. When this happens, part of the sun's light is blocked. The sky slowly gets dark as the moon moves in front of the sun. When the moon and the sun are in a perfect line, it is called a total eclipse.

The sun is the brightest object in the sky. Looking directly at the sun or even near to the sun can cause damage to the part of your eye called the retina, which can lead to blindness.

It is never safe to look at the sun directly. People have suffered eye damage after gazing at eclipses for as little as 5 seconds.

There is a strong temptation during a solar eclipse to stare at it. Many people who damage their eyes by looking directly at the sun do so during an eclipse. RNIB is particularly concerned about the safety of children's eyes during the eclipse as many children have damaged their sight because they accidentally looked directly at the sun during an eclipse.

The total eclipse, when the moon totally covers the sun, lasts a very short time. Anyone who looks at the total eclipse risks lasting eye damage because the sun emerges again without warning.

The RNIB, the Royal College of Ophthalmologists, the College of Optometrists and the Association of Optometrists and all are agreed that direct viewing of the sun during an eclipse is hazardous. The safest way of viewing the eclipse is by indirect viewing (e.g. by using a pinhole viewer).

A ‘pinhole viewer’ is an indirect way of viewing an eclipse. A pinhole viewer is made from two pieces of cardboard, one of which has a pin sized hole in it. The card with the pinhole in is used to cast the image of the sun on onto the second card which should be placed a half-metre or more from the first. Do not look directly at the sun through the hole.

It is important to keep an eye on children while using pinhole viewers in case they forget and look directly at the sun.

See the 'How to make a pinhole viewer' section at the end of this factsheet.

You may have seen, or been offered, a pair of cardboard spectacles to view the eclipse.

These viewers are often called "mylar specs" after the material used by scientists. Scientists and astronomers observe eclipses for scientific reasons and they use specially constructed equipment including aluminised mylar manufactured specifically for solar observation. This material lets less than 0.003% of the sun's light through, and no more than 0.5% of near-infrared radiation.

There are concerns about amount of protection offered by some of these publicly available "viewing specs" because:

If you do decide to use a solar filter or a pair of eclipse viewers you do so at your own risk. If you do choose this method, the Department of Trade and Industry advises that the viewer should bear a CE mark and should come with full instructions for use. The CE mark means that the viewer has been approved under the personal Protective Equipment Directive, and conforms to the Standard EN 169:1992

Ensure that the viewer fits closely to your face and does not allow the sun’s harmful rays to reach your eyes. Remember - looking at the sun directly can cause serious eye damage or blindness and the safest way of viewing the eclipse is indirectly using a pinhole viewer.

It is not safe to look directly at the sun through exposed film, or smoked glass.

It is not safe to look directly at the sun through sunglasses, even good quality sunglasses (those that are UV400 or UV 540 and conform to British or European safety standards).

Looking at the sun through a telescope or binoculars will increase the power of the sun's harmful rays and would almost certainly lead to serious eye damage or blindness.