This afternoon I was sitting at my desk working when I noticed that the sun was shining through some slots in the blinds creating dappled light on the storage cabinet just outside my office door. The dappled circles were overlapping. The circles made by dappled light are actually projections of the sun. They are round because the sun is round, and the cracks through which the sun is shining are acting like pinhole cameras. During a solar eclipse, the dapples are not round at all – rather they are circles with moon-bites taken out of them.
When I was finishing up my masters degree in 1995, I had to go to the university offices to fill out the application to graduate. There was a solar eclipse going on, and the trees were casting thousands of dappled crescents on the ground. If that happened to me today, I would probably have a camera handy, but back then I was not in the habit of carrying one with me everywhere I went.
Today things are different. When I saw the dappled light, I opened the blinds. Then I grabbed a large sheet of paper from my bookcase, poked a nice round hole in it, and taped it to the window. I needed a large sheet of paper so that it would block enough light for the pinhole effect to manifest itself. The first hole I made was indeed a pinhole, but it was too small. I enlarged it by jamming a Phillips screwdriver into it – all the way up the shaft.
I wanted a round hole – though I don’t think that’s absolutely necessary. I’ve projected the sun using my fist before. Just make an OK sign with a small opening in your fingers and rotate your hand around while watching its shadow. Eventually, the light will seep through a crack in your fist and you’ll see the sun’s projection on the ground.
The storage cabinet was about 15′ from the window, and the projection I was getting through my screwdriver hole was about an inch and a half around. And I could see sun spots. Or sun stripes. I watched for a few minutes. Then I remembered my camera.
I wanted a better screen than the beige metal surface of the storage cabinet, so I taped a sheet of paper over the projection. Then I took several shots. Here are three of them in a slide show.
I scaled and cropped them in an attempt to get them all looking roughly the same. I watched a few minutes as the sun’s image traveled across the paper.
Check out those stripes! It looks more like Enceladus than Sol. I ought to study up on pinhole cameras and see if I can improve the focus. I’m guessing better focus can be achieved by altering the diameter of the pinhole in relation to the distance between the pinhole and the projection screen.