Astronomy was closely associated with the early history of Australia for it was his first expedition to observe a transit of Venus in 1769 that Captain James Cook made the exploration of the east coast of Australia which led tothe foundation of the Colony in 1788.
With Captain Phillip's first fleet, too, there was an astronomer, Second Lieutenant William Dawes. One of his duties was to establish a station to observe the expected return of a comet.
Halley had conjectured that two comets, one observed in 1532 by Appian and the other in 1661 by Hevelius, were identical and that a new return would occur in about 1790. Maskelyne, the Astronomer Royal, was anxious to have a watch kept for the comet because at this stage the only predicted return of a comet which had been verified was the famous one of Halley and the only other body added by observation to the classical members of the solar system was the planet Uranus. Halley's conjecture was probably wrong for the comet was not observed by Dawes or by astronomers in the northern hemisphere, where it should later have been seen to better advantage. No astronomical Parramatta work is known to have been done by Dawes which is scarcely surprising, since, as well as being changed with the care of a small garrison, he was an active member in the exploration and preliminary survey of the young colony.
The astronomical tradition so began was continued by Governor Sir Thomas Brisbane when he erected his private Observatory near Government House in Parramatta in 1821. With him he brought two assistant, Charles Rumker and James Dunlop, and together they laboured on pioneering work, on the southern skies. The main instruments were a transit instrument of 3¾ inches aperture, a 2 feet mural circle, a 3¼ inches equatorial and 2 pendulum clocks. There were many useful smaller instruments and a library.
When Brisbane left N.S.W. at the end of 1825, the instruments were sold to the Government, and Rumker, who had left Parramatta in the middle of 1823 to live on his farm near Picton, and was appointed to take charge of the Observatory where his observations began again May, 1826. He returned to Europe early in 1829 and took up the post of Superintendent of the Nautical School of Hamburg and Director of Hamburg 0bservatory where he had a successful career.
Dunlop, who, after leaving the Observatory in 1826, worked privately, at his house at Parramatta and then in Brisbane's Observatory in Makerstown, Scotland, was appointed Superintendent of Parramatta Observatory towards the end of 1831. His observation, began in June 1832. Although in the years immediately after this many observations were made with the transit circle and the mural circle few of them appear to have been reduced and none was published. In later years the Observatory and its work entered on a period of such decay that Earl Grey wrote from Downing Street on 1846, October 3, to Sir Charles Fitzroy asking him to call upon Dunlop for a report immediately, and in future annually, on the work and condition of the Observatory and to appoint a commission to examine the Observatory every year "in the same manner as is practised in the Royal Observatory in this country" He concluded "you will also endeavour yourself to inspect the Observatory and to report to me in what state it appears to reason to believe that the observer pays proper attention to his duties." The commission, appointed. in 1847, April, consisted of Captain Phillip Parker King, R.N., son of a former Governor of N.S.W. and afterwards Rear Admiral, Colonel A, Gordon, Commanding Royal Engineer, and R. Rodgers, Ordinance Storekeeper.
Events now moved quickly towards the final abandonment of Parramatta 0bservatory. On 1847, June 26, King, Gordon and Rodgers submitted their report on the Observatory as a result of the inspection made on June 21. The building, of wood, was in a "dilapidated state of repair.... the floor and partitions....entirely destroyed the white ant and	it was urgent to take measures to secure the instruments from further injury". On 18th August, James Dunlop tendered his resignation to the "Board Of Visitors of Parramatta 0bservatory". In this he refers to the inadequacy of the instruments and of the building which when built in 1821 was "only intended as a private establishment not calculated to last behind a few years "The library was, he said, in "much the same state as when took charge of it in 1832". The Observations made " consist of right ascensions and polar distances with moon culminating stars, comets, etc. The reductions of a portion of the observations between and 1832 and 1835 have been, proceeded with, but having no assistant or clerk, have not proceeded so far as I could wish". He concluded "it is my wish to try a change of scene and occultation and with what little health and strength remains, to endeavour to weather it a few years longer". His wish was not fulfilled as he died on 1848, September 23.
Upon Dunlop's resignation Gordon and Rodgers recommended (1847, August 23) that instruments and books belonging to Parramatta Observatory should be packed incases and stored. This was done but the ultimate disposal was discussed over a period of years. There were at various times suggestions that they should be sold, returned to England or used as a nucleus to assist the foundation of a new institution. They remained in Ordinance Stores and thanks to the care of Phillip King were kept in reasonable condition and eventually were handed over to Sydney Observatory.