Telescopes from the Ground Up

A hobbyist turns mirror-making into an art

Sir William Herschel was a German musician living in Great Britain who became obsessed with astronomy. He began by putting together refracting telescopes from lenses and tubes that he bought, but quickly decided that refractors were too long and clumsy to handle.

He then rented a small reflecting telescope, hoping it would be easier to handle. Pleased, he asked about buying a larger reflector, only to find that none existed. There was only one thing to do: Herschel decided to build his own.

With the help of his sister, Caroline, who joined him in England in 1772, William began experimenting with making mirrors and building reflecting telescopes.

Their house became a workshop. William mastered the making of the parabolic metal mirror and came up with a better alloy by increasing the amount of copper in the mixture. The new alloy reflected 60 percent of the light that hit it, a big improvement. William’s dedication was astounding: Once, Caroline reported, her brother went 16 hours without taking his hands from a mirror he was trying to finish.

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Early Reflectors
Map of Bath, UK, where Herschel did much of his work.
See major discoveries of this telescope.
Illustration of Herschel's 20-foot-long reflector.Enlarge picture
Herschel’s 20-foot-long reflector
Year completed: 1789
Telescope type: Reflector
Light collector: Metal mirror
Mirror diameter: 19 inches
(48 cm)
Light observed: Visible
Discovery Highlights:
  • Discovered the planet Uranus.
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