TELESCOPES AND OBSERVATORIES

Compiled by Chilman Sahni

The following are the world’s most famous telescopes and observatories:

Royal Observatory, Greenwich, London

Founded by King Charles II in 1675, but atmospheric and light pollution in London reduced its efficiency. In 1884 the Prime or Greenwich Meridian, 0°, which passes through the Observatory, was adopted as the basis for all mapping and measurements. Longitude measurements refer to west or east of the meridian.

Herschel’s “forty-foot” reflector, Slough

A giant telescope built in 1788 with a 1.2 m mirror.

Birr Castle, Co. Offaly, Ireland

The Earl of Rosse’s 1.8m reflecting telescope, built in 1845, was used to discover the spiral form of galaxies. It was the world’s largest until the opening of Mount Wilson and it was recently restored and opened to the public.

Yerkes Observatory, Williams Bay, Wisconsin, USA

This 1m telescope is the biggest refracting instrument made up to this time. It was completed in 1897.

Mount Wilson Observatory, California, USA.

The telescope was installed in 1917 with a mirror size of 2.5m. It was the World’s largest until the Hale.

Hale Telescope, Palomar Observatory, California, USA.

The Hale’s 5m telescope was first used in 1949.

Jordell Bank, Cheshire

Britain’s first and once the World’s largest radio telescope, with a 76m dish, began operating in 1957.

Arecibo Observatory, Puerto Rico

Completed in 1963, this is the world’s most powerful radio telescope. Its uses include searching for pulsars and quasars and the search for alien life forms under the SETI (Search for Extra-Terrestrial Intelligence) programme. Its giant 305m dish features in the final scenes of the James Bond film Golden Eye (1995).

Hubble Space Telescope

The HST was launched in 1990 and orbits 600km above Earth’s atmosphere. It can photograph distant objects with ten times the detail possible with ground-based telescopes.

Keck I & II Telescopes, Mauna Kea Observatory, Hawaii, USA

The 2 Keck telescopes were opened in 1992-96. They are situated 4,000m up a Hawaiian mountain, so above 40% of the Earth’s atmosphere. They are the world’s most powerful ground-based instruments, with a 10.2m total aperture made up of 36 hexagonal mirrors.

Hobby-Eberly Telescope, McDonald Observatory, Texas, USA

This telescope is designed to collect light for spectrum analysis rather than for visual exploration. In operation since 1999, it has an overall diameter of 11m, making it one of the largest optical telescopes ever built.

FIRST TELESCOPES

 The first telescopes were first made in 1608 by Dutch optician Hans Lippershey. Italian astronomer Galileo built his own soon after and used it to discover Jupiter’s moons. The earliest type of telescope, known as refracting telescope, produced a slight distortion of images (called aberration). Since about 1670, astronomers have preferred to use reflecting telescopes, which use mirrors that compensate for the distortion.

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