Sydney Observatory

The Sydney Observatory is a heritage-listed meteorological station, astronomical observatory, function venue, science museum, and education facility located on Observatory Hill at Upper Fort Street, in the inner city Sydney suburb of Millers Point in the City of Sydney local government area of New South Wales, Australia. It was designed by William Weaver (plans) and Alexander Dawson (supervision) and built from 1857 to 1859 by Charles Bingemann & Ebenezer Dewar. It is also known as The Sydney Observatory; Observatory; Fort Phillip; Windmill Hill; and Flagstaff Hill. It was added to the New South Wales State Heritage Register on 22 December 2000.

The site was formerly a defence fort, semaphore station, time ball station, meteorological station, observatory and windmills. The site evolved from a fort built on 'Windmill Hill' in the early 19th century to an observatory within the following 100 years. It is now a working museum where evening visitors can observe the stars and planets through a modern 40-centimetre (16 in) Schmidt-Cassegrain telescope and an historic 29-centimetre (11 in) refractor telescope built in 1874, the oldest telescope in Australia in regular use.

The site of the Sydney Observatory has been a significant place in Sydney and has undergone a number of name changes. It was known as Windmill Hill in the 1790s when it was the site of the first windmill. After 1804 references are made to it as Fort Phillip or Citadel Hill, referring to the construction, but never completion, of a citadel on the site at Governor King's instruction for use in the case of an insurrection in Sydney. This was prompted by an influx of "Death or Liberty" Boys after the abortive 1798 uprising in Ireland, some of whom he believed to be of the most desperate character and cause for constant suspicion. Construction began but the citadel was not completed until Bligh had been installed in office. There were further discussions about a citadel during the Macquarie period but nothing eventuated beyond a half-built powder magazine, Francis Greenway's first work after his appointment as civil architect in 1815.

In 1797, early on during the European settlement of New South Wales, Australia, a windmill was built on the hill above the first settlement. Within ten years the windmill had deteriorated to the point of being useless; the canvas sails were stolen, a storm damaged the machinery, and already by 1800 the foundations were giving way. The name of Millers Point remembers this early land use.

In 1803, Fort Philip was built on the site under the direction of Governor Hunter to defend the new settlement against a possible attack by the French and also from rebellious convicts. The fort was never required to be used for any such purposes. In 1825 the eastern wall of the fort was converted to a signal station. Flags were used to send messages to ships in the harbour and to the signal station on the South Head of the harbour.

The site was known as Flagstaff Hill during and after the Macquarie era. A flagstaff had been erected on the site by 1811. Flag signalling was a cumbersome process and Commissioner Bigge advised Macquarie that it was expedient to erect a semaphore at South Head and Fort Phillip. The flag and semaphore were used for signalling in a variety of combinations.

An early observatory was established in 1788 by William Dawes on Dawes Point, at the foot of Observatory Hill, in an ultimately unsuccessful attempt to observe in 1790 the return of a comet suggested by Edmond Halley (not Halley's Comet but a different one).

In 1848, a new signal station was built by the Colonial Architect, Mortimer Lewis, on top of the fort wall on Windmill Hill. At the instigation of the Governor, Sir William Denison, it was agreed seven years later to build a full observatory next to the signal station. The first Government Astronomer, William Scott, was appointed in 1856, and work on the new observatory was completed in 1858.