Timeline: Seeing better

1608 Invention of the telescope. Claimed by Dutch lensmaker Hans Lippershey, although others (including Jacob Metius and Zacharias Janssen) are also sometimes credited.

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GALILEO’S TELESCOPE | Istituto e Museo di Storia Della Scienza

1609 Galileo improves the telescope and begins using it for astronomy, starting with lunar observations.

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Source: Gary Brown/Photo Researchers Inc

1611 German astronomer Johannes Kepler designs a new telescope using convex lenses.

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1616 A concave reflecting telescope is built by Niccolo Zucchi, an Italian Jesuit and physicist.

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Source: SPL/Photo Researchers Inc

1655 Dutch scientist Christiaan Huygens discovers Saturn’s rings and its moon Titan using a Keplerian telescope with an 11-foot focal length.

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1663 James Gregory, a Scottish mathematician, describes a new type of reflecting telescope.

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Source: Jim Sugar/Corbis
1668 Isaac Newton invents a small but powerful reflecting telescope using mirrors.

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1672 Laurent Cassegrain, a French priest, invents a reflecting telescope based on Gregory’s principles.

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1675 King Charles II commissions the Royal Greenwich Observatory in England.

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1781 Astronomer William Herschel uses a reflecting telescope to discover the planet Uranus; he later builds more powerful telescopes with which he discovers several moons of Uranus. Herschel’s largest telescope has a focal length of 40 feet.

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1839 Harvard College Observatory is established in Cambridge, Mass.

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Source: Wolfgang Steinicke
1845 In Ireland, William Parsons builds the Leviathan, a reflecting telescope with a mirror that is 6 feet in diameter. He uses it to discover the spiral structure of the nebula M51.

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1908 The Hale reflecting telescope is constructed atop Mount Wilson in California. At that time, it was the world’s largest telescope.

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1917 The 100-inch Hooker reflecting telescope is completed at Mount Wilson. It ranks as the world’s largest telescope for the next 30 years.

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1937 Grote Reber, an American radio engineer, builds the first telescope designed to observe the radio region of the electromagnetic spectrum.

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1946 British astronomer Martin Ryle builds an interferometer for making radio observations of space.

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Source: Bettman/Corbis

1948 The 200-inch Hale reflecting telescope is built at the Mount Palomar observatory in California.

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Source: Raymond S. Kleboe, Hulton-Deutsch Collection/Corbis
1957 A 250-foot radio telescope is completed in England at the Jodrell Bank Observatory,  which was established by Bernard Lovell in 1945.

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1959 Optical telescopes are launched into space on the Vanguard II satellite.

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1967 Construction begins on an observatory complex atop Mauna Kea on the Big Island of Hawaii.

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1968 The 10-meter Whipple telescope is built at Mount Hopkins in Arizona to study gamma rays.

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1980 The Very Large Array of radio telescopes is completed near Soccoro, N.M., by the National Radio Astronomy Observatory.

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1989 COBE — the Cosmic Background Explorer — is launched, designed to measure the cosmic microwave background radiation.

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1990 The Hubble Space Telescope launches from the space shuttle Discovery. The first of NASA’s four Great Observatory telescopes, it is designed to collect information from the ultraviolet through near-infrared portions of the electromagnetic magnetic spectrum.

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Source: NASA
1991 NASA launches the Compton Gamma Ray Observatory, the second in the Great Observatory series.

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1993 The first of the twin 10-meter Keck telescopes on Mauna Kea —the largest optical and infrared telescopes — is completed.

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Source: Roger Ressmeyer/Corbis 1996 The second of the Keck twins is completed.

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1997 The Hobby-Eberly Telescope is built at the McDonald Observatory in Texas, testing a new cost-effective instrument design.

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1999 The Chandra X-ray Observatory, the third Great Observatory, is launched from the shuttle Columbia.

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2001 NASA launches the Wilkinson Microwave Anisotropy Probe to map background radiation. Data it collects help revise the universe’s age to 13.7 billion years.

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2003 The Spitzer Space Telescope, the last Great Observatory, launches via a Delta rocket. It measures the thermal infrared portion of the electromagnetic spectrum.

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2009 The Planck telescope, set to launch in mid-May, will measure radiation left over from the Big Bang with high precision ( SN: 4/11/09, p. 16 ).