Telescopes from the Ground Up

Newton’s Reflector

Despite all of their new features, Newton’s telescopes had some of the same problems as earlier telescopes. The chromatic aberration was gone, but the spherical aberration remained. Newton knew that the spherical shape of the mirror caused the blurry image, but the technology of that time left him unable to grind a mirror in any other shape.

Newton’s telescope design also created a brand-new problem — the copper and tin mirrors tarnished quickly and had to be polished often. In addition, Newton’s mirrors reflected only 16 percent of the light they encountered. Refractors still produced much brighter images.

By creating a telescope that depended on reflection, Newton had launched a whole new branch of telescope design. From that point on, reflecting telescopes and refracting telescopes would be in constant competition, a technological battle for the best view of the sky.

In a nutshell...

Sir Isaac Newton replaced the main lens of a telescope with a mirror, creating the reflecting telescope.

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