Number 13: Solargraphy

Solargraphy is a way of tracking the suns movement across the sky usually using pinhole cameras. Its really easy to set up but the best images take months to collect, so you need some patients for this one. Its also best to start them when the sun is highest or lowest in the sky. And since we are only a couple of weeks away from the summer equinox (or winter equinox in the southern hemisphere)  now is an ideal time to get your solargraphic cameras ready so they can be deployed on 21st June.

You can collect some absolutely stunning images so its well worth having a go. For example here's six months from my bedroom window. And for more solargraphs take a look at Deigo's awesome collection at solarigrafia.com.

You'll need:

• A black film canister (or some other light tight container)
• Photographic paper
• Electrical Tape
• modelling knife
• A drink can
• Double sided tape
• A pin or needle
• Fine sandpaper

and in six months time you'll need

• a scanner ( or at a push a digital camera will do)

What to do
1. Cut a small square out of the side of the canister.

2. Cut  a square of tin out of your drink can. The square of tin needs to be significantly larger than the hole in the film canister.

3. Take the pin and gently push down on the tin square. DON'T push it all the way through, you just want to make a dimple on the opposite side of the tin.

4. Turn the tin square over and sand down the dimple.

5. Turn the tin over and gently push the pin in again, turn it back and sand down the fresh dimple. Repeat this 2 or 3 times until you have a very small hole in the tin.

6. Tape the square of tin over the hole in the canister (using the electricians tape). Make sure the pinhole is near the middle of the hole in the canister. 

EDIT: @solarigrafia pointed out that it hot countries you need more tape than I used here otherwise you end up with it melting and the pinhole falling off. So you might want to wrap the tape right around the canister. 

7. Do the next bit in subdued light (I didn't because then I couldn't show you the photos). Cut a section of photographic paper that's about  the circumference of the canister in length by a little under the canister's height. The paper needs to fit neatly inside the canister. Stick the paper to the canister (with the double sided tape), otherwise it rolls up over the course of the exposure. 

TOP TIP: Double and triple check that the paper is the right way round in the canister. The light sensitive side needs to be facing and opposite the pinhole. I've got that bit wrong before and there is nothing more annoying that coming back to the canister 6 months down the line and discovering you've made that school boy error.

8. Put the cap back on the canister and and if you want belts and braces tape it up.

9. Leave the canister facing out of a window, preferably south facing if you are in the northern hemisphere or north facing if you are in the southern hemisphere.

Top tip 2: Try putting your new pinhole camera somewhere overlooking a building site.

10. Wait for 6 months.

11. Take down the canister, open it up and scan the image. It will be a negative so you'll have to invert the image with some processing software. Anyway, I'll talk you through all that in six months time.

What's going on?

Remember the camera obscura? Well the same thing is going on here. Except this time we have some photographic paper to record the image. The pinhole lets in a tiny amount of light and the paper is actually quite insensitive to light (unless you use developing chemicals, which we aren't) so most of the paper needs a really long time to register  any image. But where the light hits the paper directly from the sun the paper is exposed much more quickly so the sun tracks are recorded really well.

We'll have a  chat about the details of the image in  6 months. But in the mean time you can take a look at my other solargraphs the solargraphy project and the solargraph group on flickr.

Now get on with it and we'll take a look at the result around Christmas time.