Galileo Galilei was a ground-breaking astronomer who discovered, among other things, several of Jupiter’s moons. To explore the skies, he relied on a telescopes that magnified objects with simple glass lenses. Although they were incredibly advanced at the time, modern telescopes have long since surpassed them. In fact, his instruments were simple enough for an amateur astronomer to build with a PVC pipe and two inexpensive glass lenses.
- Time: 2 hours
- Cost: $28
- Difficulty: Easy
- Measuring tape
- Hot-glue gun
- 50 mm double concave lens, 150 mm focal length
- 50 mm double convex lens, 1000 mm focal length
- PVC pipe, 5-foot length, 2-inch inner diameter
- PVC external end cap for 2-inch-diameter pipe
- Paper-towel or toilet-paper tube
- Calculate the distance between lenses: Subtract the focal length of the concave lens (curves inward) from that of the convex lens (curves outward). We got 33.5 inches. Saw the PVC pipe to this length.
- Drill a hole in the center of the end cap. Center and glue the concave lens on the inside of the cap. Put the cap on the pipe.
- Glue the convex lens to the inside of the cardboard tube. If necessary, cut a slit in the tube so the lens fits. Slide the tube into the open end of the PVC pipe.
- Peer through the hole in the cap at a target you can’t see from several feet away, such as a piece of text. If the focus is off, adjust the lens, and then glue it in place.
- If you’d like a fancier instrument, then decorate your telescope, but make sure to protect the lenses. We spray-painted the Popular Science telescope gold and attached it to a retro tripod.
This article was originally published in the January/February 2017 issue of Popular Science, under the title “Stargaze Like Galileo.”