Make an Eclipse Telescope in 10 minutes!

Here’s my take on building a simple pinhole telescope for viewing the eclipse next month. This should be a fun project for science-inclined kids of all ages — but given the subject matter, it isn’t a rainy-day project!

You will need a mailing tube (the longer the better), aluminum foil, a white paper plate, strong scissors, and hot glue.

Cut a trapezoidal slot near one end of the tube. This will be your viewing port. You may need to use a razor knife or hand-saw if the tube is thick.

Trace the end of the tube on the paper plate.

Cut out a circular white end-cap. This will be your viewing screen.

Hot-glue the screen in place onto the end near the hole you just cut. Start with a few dots of glue at the top, carefully position the end-cap, and then glue the edge a few inches at a time. If you try to do it all at once, the glue may cool too much.

Cover the other end of the tube with foil, and poke a tiny hole in it with a pin. The smaller the hole, the sharper the image of the sun.

This is just my first shot at a good pinhole, and I used tinfoil because it was handy. Experiment with other materials and different hole-making techniques — if you find something that works really well, let me know!

Mount the telescope on a tripod for ease of aiming. I just rigged a mount using two chopsticks and some scrunchies stolen from She Who Must Be Obeyed.

Take your telescope outside and point the pinhole end at the sun. You can use its shadow to roughly aim it; when the shadow of the telescope tube is circular, it’s pointed in the right direction.

Look into the viewing port and you should see the image of the sun on the paper plate. The longer the tube, the larger the image will be.

You can calculate the size of the image this way: Take the diameter of the sun (864,576 miles) divided by the distance to the sun (92,960,000 miles), which equals 0.0093. The image size will be 0.0093 times the length of the tube — in my case, 31.5 inches. So the image is .293 inches wide. The inside diameter of my tube was 4", and I quickly measured the pixel size of the tube and image — 53 out of 718 pixels, multiply that by 4" and you get .295 inches.

How long can you make your telescope? I’ve got some PVC pipe in the garage… Hmmm… :)

PS: if you want to go a little higher-tech, Meade is selling a simple reflector with an eclipse filter and two eyepieces for about $80. You can get it on Amazon.