Sir William Herschel

Of all telescope makers struck with aperture fever, Sir William Herschel tops the list! After discovering the refractors of his day were limited to a small size because of the impurities in the glass, he rented a 2" Gregorian reflector. Shortly thereafter, William was struck with a massive case of aperture fever was making his own telescopes in a very, very big way. His house in Bath was soon filled with the accouterments of mirror and telescope making. He began experimenting with different ratios of material for making the mirror blanks themselves, eventually settling on a mixture of 70% tin and 30% copper.

Each instrument that was used on a regular basis had two mirrors. One was polished while the other was used in the 'scope. The instrument William used to discover the planet Uranus was a 7-foot instrument. He used many high powers to view the stars, powers that were unheard of by his contemparies: 460, 932, 1536, 2010 and et cetera. These powers were typically used by William, even though at that time high power was approaching 300! Members of the Royal Society wee impressed when William brought his telescopes to London. Testing them against the telescopes at the Royal Greenwich Observatory, it was found that William telescopes exceeded even these!

Although William quit his day job as a professional musician when George III of England became his patron, he was forced to turn to telescope sales to supplement his income. His telescopes were the finest of his age, built by himself and his family. Caroline Herschel assisted with telescope making every step of the way, from rough grinding to fine polish. During the summer thier brother Alexander would travel from Bath to work eyepieces and other parts of the telescope.

The actual number of telescope William constructed for his own use is unknown, as well as the actual number of telescopes he made for sale. During his lifetime it became popular to own a telescope made by William Herschel. He left a list of some sixty telescopes that he made for sale, but it was not complete. The number of telescopes actually made by William Herschel is something over 420 telescopes! Although William did not build more telescopes than some other telescope makers, his desire for newer and bigger telescopes (we say aperture fever) was astronomical!

William's finest telescope had an aperture of of 18.9" and a 20-foot tube. This instrument was later taken to the Cape of Good Hope by William son's, John, and used to survey the southern skies. Herschel's rabid desire culminated in a 40-foot instrument. This instrument was massive, weighing 2118 pounds!

Information on William can be found using the links below:

William's Herschel Society, Bath, UK
Read more about William and his family - from Encyclopedia Brittanica online
William Herschel Photo Gallery

In addition to being an avid telescope maker, William was devoted observer. In fact, the desire to make more detailed observations drove his quest for ever increasing aperatures. William kept his own catalog of objects he observed and so is credited with many discoveries. William Herschel's Catalog of Deep Sky Objects is available on-line. In addition, the Astronomical League sponsors the Herschel 400 Club.

William's Monster Telescope was the largest in the world when it saw first light in 1789!

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Last Modified 5/30/06

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