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Early Telescopes
Astronomy, the study of the
heavens can be dated back to 1609. In the winter of that
year in Padua, Italy, a professor of mathematics, Galileo Galilei,
made a telescope. He became the first person to see the
mountains on the Moon, the four large moons of Jupiter, and the
phases of Venus. His observations helped convince him and
others that the Sun, and not the Earth, was the center of our
planetary system.
Galileo's telescope used a
pair of lenses to gather light and produce a magnified view of the
heavenly bodies. This type was called a refractor, because
the path of light was refracted, or bent, as it passed through the
lenses. Galileo left many sketches and detailed notes as a
pioneer of astronomy.
The early refractors,
suffered from several defects, which blurred the image. To
improve the image quality, an English scientist Isaac Newton in
1668 built a telescope that used a concave (dish-shaped) mirror to
gather and focus light. This telescope was a great advance
because it did not suffer from lens defects. This type of
telescope, called a reflector, is the one used mostly by
astronomers today.
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