Stu,
I don't know if any of the info below will help with your question but I'll post anyway..
Perhaps ask that same question in the Venus Transit thread (in Celestial Events Forum)?
I've seen people asking solar safety questions in there and being answered well.
http://www.abc.net.au/science/articl...23/3508538.htm
Quote:
Protecting your eyes
The Sun is a bright source of electromagnetic radiation, which includes visible light, infrared, ultraviolet and x-rays.
Our eyes normal reaction when we glance at the Sun is to look away. This reflex reaction protects the retina, a layer of cells lining the back of the eye.
These cells collect light and convert them to electrical signals, which are sent to the brain. Intense exposure to electromagnetic radiation can destroy the cells, and cause permanent eye damage, so it's important to protect your eyesight while viewing any astronomical phenomenon involving the Sun.
Direct viewing
You can view the Sun directly by using specially made filters. Do not use sunglasses, smoked glass, exposed film or CD/DVDs as filters. While these objects may reduce the amount of visible sunlight your eye receives, they don't significantly reduce the amount of UV light or x-rays
Specially manufactured solar viewing glasses reduce all forms of light that are known to cause damage to the eyes. But it's important to note that while these glasses typically meet European and US safety standards, there are no Australian/New Zealand standards for solar filters. Also be aware that they are made of a thin polymer plastic that can be scratched or damaged. Do not use the filter if you suspect it is damaged.
An alternative is number 14 (or greater) welding glasses. If the glasses have been damaged, or you are unsure of their rating, do not use them.
If you own a telescope, there are a range of solar filters available such as Baader film and Hydrogen-alpha. The latter type allows you to see the structure of Sun, such as prominences and flares, in fine detail. You should only use filters that attach to the front of the telescope, which filter light before it enters the tube. Do not use filters that attach to the eyepiece.
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