Sydney Observatory is located on a hill now known as Observatory Hill in the centre of Sydney. The site evolved from a fort built on ‘Windmill Hill’ in the early 19th century to an astronomical observatory during the nineteenth century. It is now a working museum where evening visitors can observe the stars and planets through a modern 40 cm schmidt-cassegrain telescope and a historic 29 cm refractor telescope built in 1874, the oldest telescope in Australia in regular use.
An early observatory was established in 1788 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 of Halley’s Cometfame. The Colony’s second observatory was established at Parramatta in 1821 by Governor Sir Thomas Brisbane.
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.
The most important role of the observatory was to provide time through the time-ball tower. Every day at exactly 1.00 pm, the time ball on top of the tower would drop to signal the correct time to the city and harbour below. At the same time a cannon on Dawes Point was fired, later the cannon was moved to Fort Denison. The first time ball was dropped at noon on 5 June 1858. Soon after the drop was rescheduled to one o’clock. The time ball is still dropped daily at 1pm using the original mechanism, but with the aid of an electric motor, not as in the early days when the ball was raised manually.