Telescopes from the Ground Up

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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Map of Venice, Italy, where Galileo did much of his work.
Illustration by Galileo of one of his refractors.Enlarge picture
Galileo’s first refractor
Year completed: 1609
Telescope type: Refractor
Light collector: Glass lens
Telescope length: 36.5 inches
(92.7 cm) long
Light observed: Visible
Discovery Highlights:
  • By systematically making observations and drawing conclusions, Galileo demonstrated and perfected the approach that would become standard practice for telescopic astronomy.