The year was 1609. Galileo Galilei turned a newfangled contraption called a spyglass—which made far away things appear close—toward the sky. He saw craters and mountains on the moon’s surface, moons near Jupiter, sunspots and the phases of Venus—all culminating with his mind-blowing assertion that the planets orbit the sun (and not vice versa). That thoroughly factual claim got Galileo dragged before the Inquisition and also formed the basis of all modern astronomy. From stars to planets to galaxies, here’s what to look for when choosing a solid, heresy-free telescope of your very own.