When you buy through links on our articles, Future and its syndication partners may earn a commission.The Yerkes one-meter refractor on display at the 1893 World’s Fair in Chicago. | Credit: The Field Museum Library/Wikimedia CommonsThe past 250 years of optical telescopes have seen revolutionary discoveries and technology that the telescope’s inventor, a seventeenth century spectacle-maker by the name of Hans Lippershey, maybe wouldn’t have believed possible.When we look back through the annals of telescope history, we find that a significant turning point came, coincidentally, just five years after the United States’ Declaration of Independence was christened.AdvertisementAdvertisementIt was back in England, in 1781. William Herschel had just made what was possibly the greatest astronomical discovery the world had seen up to that point: a new planet, Uranus. The fact that Herschel had found a seventh planet from the sun was revolutionary in itself. All the other planets, from Mercury to Saturn, had been known since antiquity, obvious in the night sky to the naked eye.Uranus, on the other hand, isn’t really visible without optical aid, and its discovery illustrated the power of the telescope to dramatically widen our vistas. Moreover, Herschel found the new planet using a 6.2-inch (157-millimeter) reflecting telescope that he had constructed himself. He was looking through it from the back garden of his home in the Somerset city of Bath.Herschel was a prolific builder of telescopes, polishing and shaping their speculum mirrors. The 6.2-inch telescope was a midget compared to some of his other beasts, including the famous discovery machine that was the 20-foot, or -meter, in focal length telescope with its 18-inch (457-mm) aperture, and the less successful 40-foot (12-meter) telescope.Herschel proved that telescopes could do serious science. “As a self-taught astronomer, William Herschel transformed the reflecting telescope from what had generally been thought of as a scientific toy into a serious scientific tool,” British science historian Robert Smith of the University of Alberta in Canada told Space.com. “At the root of all Herschel’s efforts is his telescope building, because he had to build these big telescopes himself.”Refractors and reflectorsTelescopes come in two main forms: the reflector and the refractor.AdvertisementAdvertisementReflectors use mirrors to reflect light to a focal point where the eyepiece is located; refractors use lenses to focus light. In the 18th and 19th centuries, British reflectors like Herschel’s were the dominant telescope category, as exemplified by those constructed by the likes of Liverpool’s William Lassell and Ireland’s Third Earl of Rosse, William Parsons. However, across the English Channel in mainland Europe, refractors, which at the time were optically higher quality, were dominant instead.”You have to distinguish what’s going on in Britain with what’s going on elsewhere,” said Smith.Lassell built reflectors with apertures of 24 and 48 inches (61 and 122 centimeters). And the great Leviathan of Parsonstown in Ireland is Lord Rosse’s own behemoth, still standing today as a UNESCO World Heritage Site. While the likes of Lassell and Lord Rosse were wealthy, self-taught “grand amateur” scientists, in Europe refracting telescopes were used by academics at universities to make precise measurements of the cosmos, from the orbits of double stars to the distance to stars using parallax.The dome of the giant Hooker Telescope. | Credit: Craig Baker/Wikimedia Commons, CC BY-SA 4.0″On the European continent, refractors were used by professional astronomers whose focus was on precision, whereas for Lassell and Rosse the focus was on collecting more light to see fainter objects,” said Smith.In comes the U.S.Building large refracting telescopes had its challenges and led to a period referred to as the “Telescope Race,” where prestige was equally a motivation alongside science. The “race” was won by the 40-inch (one-meter) refractor at Yerkes Observatory in Chicago in 1897, which cost $500,000 at the time (about $20 million in “I have argued that in the 1880s, America was a bit of an astronomical backwater compared to Europe, but by the 1920s the United States had become the leading nation, certainly in terms of observational astronomy,” said Smith.It wasn’t just Yerkes. In California, wealthy landowner James Lick founded the Lick Observatory on Mount Hamilton after being dissuaded from his original plan to build a giant pyramid as a monument to himself in downtown San Francisco. Percival Lowell, obsessed with his delusions about canals on Mars, founded the Lowell Observatory in Arizona in 1894. And on Mount Wilson in California, something big was stirring in part thanks …
