Telescopes from the Ground Up

Now that it had become possible to create larger glass lenses free from chromatic aberration, the telescopes known as achromatic refractors began to grow in popularity and size. As the diameter of the primary lens increased, refractors again expanded in length to accommodate this larger lens. The bigger the lens, the more light it could collect, and the fainter the object the telescope could see.

Get to the root of it

Because the refractors’ glass lenses were so much better at collecting light than the tin and copper mirrors of reflecting telescopes, refractors remained the instrument that provided the sharpest view.

Picture that

The dawn of photography in the early 1800s opened up a new era for telescopes. In 1840, an English-American chemist and photographer, John William Draper, focused the Moon’s image on a light-sensitive photographic plate, using a clockwork device to keep the light in place even as the Earth rotated and the Moon moved through the sky. After an exposure of 20 minutes, he had taken the first-ever photograph of the Moon.

Within the decade, the technologies of photography and of tracking celestial objects would migrate to telescopes, enhancing them dramatically. Now images could be recorded without endless sketching, and faint objects could be more easily observed. The first telescope to use the new technology was a refractor.

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