Italian astronomer Galileo Galilei peered through his newly improved 20-power homemade telescope at the planet Jupiter. He ...

The first spectacles, designed to correct farsightedness ... "objective" lens—the convex lens at the far end of the telescope—Galileo ground a lens larger than he needed, for example.

Still, even Galileo recognized the ground-based uses of telescopes. After building his first telescopes, Galileo demonstrated the new instrument to the Venetian Senate, including military leaders.

Galileo Galilei, with a homemade telescope, noticed three points of light near Jupiter. Initially believing they were distant stars, Galileo’s repeated observations over several nights and realized ...

Second, you soon want a bigger telescope. Galileo, who first trained a telescope on the night sky 400 years ago this fall, pioneered this two-step program. First, he marveled at what he could see.

January 7, 1610, using a hand-built telescope, Galileo Galilei discovered the planet Jupiter and four moons orbiting the planet. His first observation led him to believe he was observing a group of ...