Solar parabolic cooker with the mechanical mathematician!

Step 7 Place the mathematician on the foiled cardboard

You should place the mathematician on the middle of the square of you solar cooker that you want to be bottom square. I then put a couple of marks on either side of the dark piece of wood in case it slips. I then put a little dot on the centres of all the other squares. 11 dots in my case.
Next you must set the length of your string line.