Telescopes from the Ground Up

Telescope-making gets complicated

George W. Ritchey made his first reflecting telescope when he was a student in college. He continued to work with telescopes, both creating mirrors and adapting existing telescopes for photography.

His expertise led astronomer George Ellery Hale to choose him to design the 60-inch reflecting telescope at Mount Wilson Observatory.

Mr. Clean

First, Ritchey built a machine to grind and polish the glass mirror. The machine combined cast-iron grinding tools, water, and a new kind of grinding material called carborundum, which was almost as hard as diamond, to grind and polish the 60-inch glass disk.

Ritchey was extremely careful to keep dust out of the polishing shop, knowing that dust on the surface of the disk during the grinding and polishing would affect its shape. He varnished the walls and ceilings and kept the cement floor wet. He sealed the windows and had the incoming air filtered. He put a canvas screen over the mirror to protect its surface from falling particles. Only the optician, dressed in a surgical cap and gown, was allowed to enter the shop. Ritchey was ahead of his time: Today important telescope parts are normally made in special dust-free environments, called clean rooms.

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Huge Reflectors

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Map of Mt. Wilson, California, USA, where the 60 inch Ritchey reflector is located.
Image of the 60 inch Ritchey reflector.Enlarge picture
Ritchey’s 60-inch Reflector
Year completed: 1908
Telescope type: Reflector
Light collector: Silver-coated glass mirror
Mirror diameter: 60 inches
(1.5 m)
Light observed: Visible
Discovery Highlights:
  • Its findings were used to demonstrate that most stars at the same temperature have the same brightness and, surprisingly, contain the same amount of matter.