History of Observatories

Astronomical observatories were built long before telescopes were invented. About the third century B.C. an astronomical observatory was built in Alexandria, Egypt. No Greek observatories are known, but some Greek astronomers, including Ptolemy, worked at Alexandria. Throughout Roman times and the decline that followed, there was little interest in astronomy and no noteworthy observatories were built. Astronomy was revived by the Arabs and in the ninth century A.D. a caliph, al-Mamun, built a large observatory at Baghdad.

In the New World, several observatories had been built by the 11th century. The earliest observatory in Europe, built at Nuremberg, was started in 1472.

The greatest of the pre-telescope observatories, called Uraniborg (Castle of the Heavens), was built in the 1570's by the Danish astronomer Tycho Brahe. The observatory had many instruments to help an observer accurately measure the positions of heavenly bodies.

After the telescope was invented in the early 17th century, observatories built for telescopes began to replace the earlier observatories. The French national observatory in Paris was established in 1671. Four years later the Royal Greenwich Observatory in England was established to aid in the determination of positions of celestial bodies for navigation. Observatories were built in almost all of the European countries. Many were part of major universities. The first observatory in the United States was built at the University of North Carolina in 1830.

Until the latter part of the 19th century, the work done at observatories was primarily determinations of positions and movements and the discovery of new celestial bodies. However, with the development of photography and the invention of instruments such as the spectroscope and the interferometer, it became possible to study both the composition and the motion of stars. For this work, larger telescopes that gathered more light were built.

The foundations of radio astronomy were laid in the 1930's, when it was discovered that radio signals were coming from space. Although some radio telescopes were built earlier, most of the large-scale building of radio observatories began in the 1950's.

The atmosphere strongly interferes with observations of some types of radiation, in particular ultraviolet radiation and X rays. A number of satellites have been placed in orbit to study stars (including the sun) and other sources of these types of radiation. One of the first such satellites was the first Orbiting Solar Observatory (OSO-1), which was launched in 1962. Others include the High Energy Astronomy Observatories launched in the late 1970's. The Hubble Space Telescope, a large optical telescope, was launched in 1989. Observations showed that the telescope's primary mirror was flawed, and in 1993 astronauts installed a corrective optical system.