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
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