Telescopes from the Ground Up

Era of Galileo's Refractor

Galileo’s Refractor

The first telescope opens a window on the universe

Galileo wasn’t the first to build the device that would become known as the telescope, but he seems to have been the first to use it to study the heavens.

In 1608, Hans Lippershey of Holland, an eyeglass maker, asked for a patent on a “certain instrument for seeing far.” One of the stories says that Lippershey got the idea for his invention when children playing in his shop held two eyeglass lenses up together and found they could see the weathervane atop a distant church.

I spy

The device, called a spyglass, was used to magnify distant objects on Earth. As soon as Galileo learned about the device, he built one and set about improving it, creating the first refracting telescope. The primary lens was convex, and the second lens, the eyepiece, was concave. Then he developed techniques for grinding and polishing the lenses and used math to calculate the distance between the lenses that would create the clearest images.

Galileo figured out that a greater distance between the lenses would let him see close objects more clearly, and that a shorter distance between the lenses would let him see faraway objects better. He also placed his refracting telescope on a stand, so he didn’t have to worry about his hands shaking while he made his observations.

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