Earlier on this year we had a partial solar eclipse that was viewable from the UK. Luckily it was cloudy as I couldn't find any of those cardboard glasses or figure out how to safely photograph the eclipse. This did, however, start me on a journey to try and figure out a cheap and easy way to safely view solar events. I remember a long time back there was a transit of Venus, which was cool also.
Searching on the web revealed that you could buy a nifty folding viewer with a lens and a mirror that projected the image onto a white sheet for safe viewing. The cardboard version was £45 which I thought was ridiculous so I set out to make my own. I started researching and pretty soon realised that a pin-hole was the ideal lens for this job. It's simple to make and cuts out an awful lot of light!
This is a bit of a free-form instructable as I'm still experimenting and changing things around to get things better. But the bottom line is that I can totally safely and fairly comfortably observe the sun, so my main objective has been met. I think so far I've spent less than £5 on materials, and most of that was in the "I'm sure I've got one somewhere but can't find it right now" category!
Step 1: Gather Materials
Here are the tools and other materials I used. Hammer, nail, emery paper and drinks can all went to make a pinhole. Not shown here is a small mirror. I couldn't find one, so bought one from ebay. It was a folding camping mirror and very cheap. The idea of using a mirror is to increase the length of the system without making it bigger, and also to bring the image to somewhere easier to view. The cardboard boxes, gaffer tape and bulldog clips are used to make a housing for the whole thing. I was lucky to have a supply of identical sized boxes available. Also, after I took these photos I found a length of black material that acted as a hood.