Telescopes from the Ground Up
Illustration of a Hevelius' refractor.

Out of reach

The greater distance between the lenses meant the telescope had to be longer. Astronomers began to design and build longer and longer telescopes, achieving further discoveries. But then the designs began to get a bit out of control. Some of the telescopes expanded to over 100 feet in length -- so long, in fact, that they could no longer be enclosed in tubes or handled easily. These wild contraptions were bare lenses attached to poles, or controlled by ropes and pulleys. The designers’ enthusiasm far outweighed practicality – one person suggested building a 1,000-foot-long telescope that would be able to see animals on the Moon.

Though the longest refracting telescopes were impressive and got a lot of attention, they didn’t work very well. They frequently suffered from mechanical failure because of their size and were too difficult to keep steady. Observations were often interrupted by the swaying and shaking of the telescope. Instead, most of the important astronomical discoveries of the period were made with 30- to 40-foot long refracting telescopes.

In a nutshell...

Telescopes with flatter lenses brought wider and clearer views of the sky, but required longer tubes. Some refractors were so long that they became difficult to maneuver.

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