SAFETY PRECAUTIONS TO OBSERVE THE TRANSIT OF VENUS
(Excerpt from “Vénus devant le Soleil”, Vuibert/Adapt, 2003 - translated for Futura-sciences).
Never look at the Sun directly with the naked eye.
Systematically check to see if your instrument for looking at the Sun, is equipped with an appropriate filter.
If you are in charge of a youth group, be even more vigilant, especially with children!
"Caution : The direct observation of the sun can cause serious lesions.In visiting this website you can not be an unacompanied minor. You must read the solar observing safety features and promise not to hold venus2004.and their authors as well as futura-sciences responsible for any problem linked to the observation of the transit of Venus.
The Filters listed below are dangerous because they may either splinter during observation or allow many infrared rays to pass through them:
Smoked glass, blackened by candles;
One or several data compact disks, CDs;
Neutral photographic filters made from glass or polymer;
Two crossed polarizing filters
Filters made from film negatives, be they black and white, colour or x-ray;
Solar filters that screw onto an eyepiece if they are not associated with a Herschel helioscope. You may reject as well, filters labelled "SUN" sold with commercial instruments (See below);
Wrappers for food products apparently similar to Mylar, but which in fact are very different;
Finally, the best precaution is: don't use any filter of which you aren't sure!
Please note: Formerly, black & white film negatives could be used as they contained silver. However, nowadays, they are non silver-bearing and are therefore unsafe and must be rejected.
The Eclipse kind of glasses from the eclipse of 1999 must absolutely not be used to watch the transit. The material used to build these glasses can be damaged or too old. These eclipse glasses are very cheap, it is recommended to buy a new pair.
FILTERS WITH WHICH TO SAFELY OBSERVE THE SUN
The best is the full aperture plated glass filter. It fits onto the front of the instrument, doesn't warm up, and is optically perfectly corrected;
Solar filters that screw onto the eyepiece associated with a Herschel helioscope;
One or several thicknesses of Mylar or AstroSolar (plastic movie film coated with aluminum plate);
Welder mask glass with maximal indication.
It is important to point out the dangers of some supposedly solar filters (labelled "SUN") sold together with almost all commercial instruments, and not only with inexpensive ones. Their user instructions are at the heart of the problem. As these filters are assembled with the eyepiece, they are therefore close to the focus and undergo a considerable warming. If you don't respect the strict observational procedures, they may splinter and immediately let devastating rays spill into your eyes. That's why manufacturers and sellers of instruments equipped with these filters recommend that one shouldn't observe with them for more than one minute. As directed, it would be necessary afterward to either cover the tube or point the telescope away from the Sun for several minutes, to allow time for the filter to cool, before starting on another sequence of observations. This is what makes the situation not honestly convenient! It opens the door to accidents: You may feel that you can follow these strict rules, but who will protect somebody else using your instrument in your absence? Will he do the same? Besides, if an ill-informed person uses this kind of filter with a telescope having a diameter larger than 80 mm, it will only need a few seconds for it to splinter rather than one minute. The best advice is, throw away these filters and look for really safe methods for your observations.