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The History of the Reflecting Telescope

The reflecting telescope was invented by Sir Isaac Newton, and proposed by a few others in the late 17th Century in an effort to solve the problem of chromatic aberration that was plaguing refractors of the time. These early reflectors used metal mirrors made from a highly reflective metal alloy of copper and tin known as speculum metal. Development of this type of telescope reached its zenith in the late 18th Century due to the efforts of Sir William Herschel, a German immigrant who settled in England. With such telescopes Sir William, along with his sister, Caroline, discovered the planet Uranus along with numerous and previously unknown nebulae (we would call them ‘faint fuzzies” today) and star clusters along with a host of newly discovered comets. Adding their observations to those of Charles Messier in France, Herschel, and others developed the first deep sky object catalogues which eventually became the New General Catalogue (NGC) still in use today. In Ireland in the 1840s, Sir William Parsons, the 3rd Earl of Rosse pushed metal mirror technology even further with the building of the 72” “Leviathan of Parsonstown”. With this telescope, Parsons became the first person to see the spiral structure of what later became known as spiral galaxies.

But reflector technology took the second half of the 19th Century to mature until silver on glass mirrors could be reliably produced. Then, even larger telescopes of up to 100” could be built with American astronomer, George Ellery Hale and his instrument maker, George Willis Ritchey leading the way at Mt. Wilson in southern California. With these telescopes, Hale and others were to make the most spectacular discoveries and setting the stage for the foundation of modern physical astronomy as we know it today.

Speaker: Dr. Ken Lum

Friday, 01/12/18


Website: Click to Visit


Free ($3 parking)

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Peninsula Astronomical Society

Foothill College
Room 5015
Los Altos Hills, CA 94022