SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/astro-newton-first-reflector

Who built the first successful reflecting telescope, in 1668?

Isaac Newton.

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  1. Galileo Galilei
  2. Johannes Kepler
  3. Isaac Newton ✔

Why: Newton used a curved mirror instead of a lens to form the image. Mirrors avoid color blur and can be supported from behind, which is why nearly every big research telescope today is a reflector.

Huh, didn't know that: Galileo's telescopes, by contrast, were refractors that used lenses.

The dad joke
Newton's telescope really reflected well on him.
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References

Answer: Isaac Newton. Newton used a curved mirror instead of a lens to form the image. Mirrors avoid color blur and can be supported from behind, which is why nearly every big research telescope today is a reflector.

  1. OpenStax Astronomy 2e, 6.1 Telescopes openstax.org/books/astronomy-2e/pages/6-1-telescopes
    The first successful reflecting telescope was built by Isaac Newton in 1668.
    Checked 2026-10-10.

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