The 1999 Mensa Total Eclipse Party
Wednesday 11th August 1999; Rethel, France

Viewing glasses will not be provided at the TEP venue. They are only of limited value anyway.

The Royal Greenwich Observatory have published a 'Guide to the 1999 Total Solar Eclipse', priced 5.99, in which there are a set of protective glasses. This book is obtainable from most reputable booksellers, such as Waterstones. I have also seen the viewers sold separately from the book, priced 3.99.

Please note that such glasses should be used with extreme caution, as the protection they afford may not be perfect. In general you should not stare at the sun's disc while it is visible, even during the partial eclipse, due to the risks of sustaining permanent eye damage or blindness. The only safe period to look at the sun is during the period of totality, which lasts only 2 minutes.

The threat to your eyesight comes not so much from the visible sunlight, but from the sun's heat which is transmitted as infrared (and therefore invisible) radiation. This radiation will pass easily through the eye's cornea (the lens) and vitreous humour (the liquid part of the eye), and quite literally burn the retina. The heat energy can permanently destroy the rods and cones, and may be even damage the retina's nervous system and blood vessels. You should therefore take great care how you observe the eclipse.

In general, the safest way to observe the sun's disc is by projection onto a suitable flat surface using a pin hole to obtain a sharp image of the sun. Further details of how to observe the eclipse safely, as edited from the NASA eclipse web site, are included in the information pack I sent out to you. If you haven't read it, you should perhaps do so before setting out for France.

One alternative suggestion I've heard of, is to view the sun's image in a tray of black treacle. The treacle will form a smooth mirror-like surface in which a bright object like the sun will be visible. This method also has the advantage of you being able to eat your 'eclipse viewer' after the event, thus leaving no waste (at least not for a while) to be cleared up. Anyone for treacle butties?

Brian, TEP Information