Protect your eyes!
Beware, watch your eyes!
It is very dangerous to observe a solar eclipse without adequate eye protection. This can result in irreparable eye damage or even blindness. NEVER look directly at the Sun. In just ten or twenty seconds, looking at the Sun (even partially eclipsed) can burn the retina and cause irreversible lesions. Children are particularly vulnerable.
Protective glasses (not ordinary sunglasses) should be used, choose only those specially made for solar eclipse observations, conforming to EU directives on individual protection, and certified by national health organisations. The safest way to observe the Sun is by projection on a screen. For more information on building a safe Solar Viewer, see below.
Build your own Solar Viewer!
ESA's Simon Dinwiddy has devised a way of viewing the Sun which is both safe and effective.
- Take the lens from a pair of +1 dioptre low-power reading glasses (available from most department stores). This lens has a focal length of 1000 millimetres (1 metre).
- Take a small piece of wood (10 cm x 6 cm x 1 cm approx.) and drill in the centre a hole of 10 mm diameter.
- Fix the lens over the hole.
- Fix the board to a long lath or rod (1 metre minimum length) with a bracket and with another bracket fix another board (12 cm x 10 cm x 1 cm approx.) exactly 1 metre from the first board. Pin a piece of white paper to the second board.
Figure 1. Solar viewer
Your completed Solar Viewer should resemble the above diagram. It is now ready to use. With your back to the Sun, place the rod over your shoulder, and aim the lens at the Sun so that the shadow of the smaller board falls on the larger board. In the middle of this shadow you will see a small (9-mm diameter) but perfect image of the Sun.
You can even see the sunspots, perfectly focussed. Look an hour later, and you may be able to see that image of the sunspots has turned, as the Earth rotates. Look again a day or two later and you may be able to see the changes in the pattern of sunspots.
Having bought a pair of spectacles, you will, of course, have another lens so make a second Solar Viewer and enjoy the eclipse with a friend!