Pinhole projector

Get ready for the 2017 Eclipse Across America!

The next eclipse will be Monday, August 21, 2017. Here at Explora, in Albuquerque, we’ll have a partial solar eclipse with the sun 73% obscured. We will have our pinhole projectors ready to safely view the eclipse! Learn more about the 2017 Eclipse Across America!

What you will need:

  • 2 pieces of white paper, card stock or plain cardboard
  • Aluminum foil (a 3-4 inch square)
  • Tape
  • Push pin or paper clip
pinhole projector

Very Important Safety Note: Never look directly at the sun without proper protection! Sunglasses are not enough protection for your eyes from the sun’s full power, even during a partial eclipse. Do not look at the sun through the pinhole projector.

Here’s what to do:

  1. Cut a square hole, approximately one inch, in the middle of one piece of card board. You can even cut up a cereal box.
  2. Cover the hole with aluminum foil. Use tape to secure the foil over the hole.
  3. Use a push pin or the end of a paper clip to poke a small hole in the foil.
  4. Set the second piece of card stock on the ground; this is your projection screen. Stand with the sun at your back and hold the other piece of card stock with the foil facing up and so the pinhole projection shows up on the screen.
  5. Make your projected image bigger by holding your pinhole projector farther away from the card stock on the ground.

Take it further:

  • Put the projection screen in a shaded area while holding the pinhole projector in the sun. Can you make your projected image more defined?
  • Try poking more holes in the aluminum foil. What kind of shapes and designs can you project onto your screen?
  • Try using a cereal or shoe box or a cylinder to make different pinhole projectors. Do you like one design better than the others? Do the projections appear to be different?
  • Try looking at different objects through your projectors. Try taking pictures through your pinhole projectors with a camera. What do you notice about the objects?

What’s going on?

The technique of using a small hole to focus light, like in your pinhole camera, dates back to the 5th century BC. The pinhole in the foil acts like a lens and diffracts the light as it passes through the hole, making the object of interest appear upside down. Since the hole is so small, only a fraction of the sun’s total light gets through and onto the projection screen. If you didn’t have a hole, light from every direction would hit the projection screen and you wouldn’t see a defined image, just a bunch of light. The hole helps block light coming from different directions and only lets through a very small, focused amount of light, allowing you to see a clear projection of the object.

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