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.

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.

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.

[4] 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.

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 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.

When Blacket resigned in 1854 to take on the design and supervision of construction of The University of Sydney, plans were underway for an observatory that would be both functional and of architectural quality.

Correspondence from him to Blacket in the early years indicates that Weaver was much happier in direct supervision of works than performing the duties of his desk-bound role.

[1] Alexander Dawson replaced Weaver as Colonial Architect in April 1856 and the new Government Astronomer, Reverend William Scott, M.A., arrived with his family in October that year.

These contributed the symmetry of the townhouse facade for the residence and an asymmetry for the observatory born of the peculiar needs of transit room, equatorial dome and time ball tower.

Russell's talent, entrepreneurial flair, intimate knowledge of how to work the political and bureaucratic system of NSW and longevity gave him a 35-year tenure as Government Astronomer and made him the Grand Old Man of physical science in the colonies.

Like his predecessors, he had been concerned with the restrictive nature of the observatory grounds which made siting of meteorological and auxiliary astronomical instruments difficult, if not impossible.

His interest in the application of photography to astronomy and a visit to Paris in 1887 prompted Russell to take part in a "great star catalogue".

Cooke was lured to Sydney from Perth Observatory with promises of a new site located in Wahroongah, then free of city lights and traffic, the purchase of modern instruments and a world trip to investigate the latest developments.

[1] Two World Wars, a great depression and a commitment to a logistically exacting astrographic program helped reduce the vitality of the establishment in the twentieth century.

A new domed building was constructed in the south-east corner of the observatory to house the Melbourne star camera that replaced the original Sydney one.

[1] These activities commanded respect for Sydney Observatory in astronomical circles, but its image in the NSW Parliament and associated Public Service remained forgettable.

The financial difficulties of the State of NSW at that time resulted in a letter from the Premier in June 1982 announcing his decision to transfer the observatory to the Museum of Applied Arts and Sciences and discontinue scientific work.

[8] The astrographic building was demolished and the dome, instruments and most of the glass plate and paper collection was removed to Macquarie University for future research use.

Furthermore, the Astrographic dome and instruments have been returned by Macquarie University to the Museum store where they are awaiting conservation and a Heritage NSW approved structure on the observatory site.

[1] The most significant change to Sydney Observatory in 50 years, the new Eastern Dome was opened on 27 January 2015, by the Deputy Premier Troy Grant and Minister for Disability Services, John Ajaka.

[1][9] Located at the Sydney Observatory is a vintage 7.25-inch refracting telescope on an Equatorial mount that was manufactured by the German company Georg Merz and Sons between 1860 and 1861.

Its dominant location beside and above the port town and, later, City of Sydney made it the site for a range of changing uses, all of which were important to, and reflected, stages in the development of the colony.

These uses included: milling (the first windmill); defence (the first, and still extant, fort fabric); communications (the flagstaffs, first semaphore and first electric telegraph connection); astronomy, meteorology and time keeping.

These include: colonial Governors Hunter, Bligh, Macquarie & Denison; military officers and engineers Macarthur; Barrallier; Bellasis and Minchin; convicts: the as yet unnamed constructors of the mill and fort; architects: Greenway (also a convict), Lewis, Blacket, Weaver, Dawson and Barnet; signallers and telegraphists such as Jones and the family Moffitt; astronomers: particularly PP King, Scott, Smalley, Russell, Cooke and Wood.

[1] The elevation of the site, with its harbour and city views and vistas framed by mature Moreton Bay fig (Ficus macrophylla) trees of the surrounding park, make it one of the most pleasant and spectacular locations in Sydney.

[1] The picturesque Italianate character and stylistic interest of the observatory and residence building, together with the high level of competence of the masonry (brick and stone) of all major structures on the site, combine to create a precinct of unusual quality;[1] Finally, the continued use of the observatory for astronomical observations and the survival of astronomical instruments, equipment (Appendix 4) and some early furniture (Appendix 3), although temporarily dispersed, and the retention of most interior spaces, joinery, plasterwork, fireplaces, and supports ensure that the observatory can remain the most intact and longest serving early scientific building in the State.

[1][19][full citation needed] Sydney Observatory was listed on the New South Wales State Heritage Register on 22 December 2000 having satisfied the following criteria.

The elevation of the site with its harbour and city views and vistas framed by the mature fig trees of the surrounding park, make it one of the most pleasant and spectacular locations.

The picturesque Italianate character and stylistic interest of the observatory and residence building, together with the high level of competence of the masonry (both stone and brick) of all major structures on the site, combine to create a precinct of unusual quality.