Telescopes from the Ground Up
Conceptual illustration of a multiple mirror telescope.

Multi-mirror Telescopes

The more mirrors the merrier

As the mid-1900s rolled around, astronomers once again hit a wall. It seemed impossible to make mirrors larger than the 200-inch (5-meter) mirror in the Hale telescope. Larger glass mirrors were flawed and likely to warp under their own weight, but bigger mirrors were needed to collect more light to see the faintest objects in space.

The invention of the computer, first developed in the 1940s for business and industry, gave astronomers the tools they needed to devise new techniques. In 1976, Russian astronomers created the BTA, the largest telescope in the world, with a single 236-inch (6-meter) mirror. The telescope was controlled and positioned by computers, but astronomers were unable to stop the giant mirror from sagging under its own weight, distorting any images it produced.

If astronomers wanted bigger mirrors, they would have to find another way.

Divide and conquer

The solution was to use many mirrors to create a single image. The many mirrors would operate together like one giant mirror, larger than 200 inches. Computers would be needed to control the shape and position of the individual mirrors, position the telescope, and track the object in the sky. These telescopes would become known as multiple-mirror telescopes.

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