The annular eclipse is fast approaching. In preparation of the May 20, 2012 event make your own pinhole projection box.
- a long box (at least 4 feet long, you can tape two small boxes together)
- a pair of scissors
- a thumbtack
- a box cutter
- a piece of white paper
- a small square of aluminum foil
One of the simplest ways to view the eclipse is to create a pinhole projector, which is a fancy term used to describe a long box with a pinhole in one end. Sunlight shines through the pinhole and an image of the Sun is projected to the far end of the box.
There are three essential ingredients that go into a good pinhole projector:
1) A long box. The longer the better. The size of the image of the Sun that the box projects is only going to be about 1/100ththe length of the box. That means that for a box that is five feet long the projected image of the Sun is only going to be a little over a half-inch in diameter. If you can’t lay your hands on a single long box, consider taping together two or more smaller boxes.
2) The hole through which the sunlight passes needs to be very small, very thin and very round. Aluminum foil makes an excellent pinhole surface; it’s thin, opaque to light, and a pushpin or thumbtack makes a near-perfect round hole in it. For our pinhole projectors, we like to start with a square hole about one inch across in the cardboard of the box, then cover the hole with a small sheet of aluminum foil. You can then carefully punch a hole in the center of the aluminum foil with a needle.
3) Use a sheet of white paper as the projection surface opposite the pinhole. The Sun and eclipse will be much easier to see on white paper than if you just try to see it on the brown cardboard of the box.
We recommend you try your box out well in advance of the eclipse. Aim your box so that the pinhole is pointed at the Sun and the image of the Sun projects onto the white paper at the opposite end of the box. If your box is projecting a nice round image of the Sun with fairly crisp edges, then you’re ready for the eclipse.