About nine years later, on 13 May 1861, Tebbutt discovered the 1861 comet, one of the most brilliant comets known. There was no means then of telegraphing the intelligence to England where it became visible on 29 June. Tebbutt was acknowledged as the first discoverer of this comet, and the first computer of its approximate orbit. In November 1861 he purchased an excellent refracting telescope of aperture and focal length, and in 1862 on the resignation of the Rev. W. Scott he was offered the position of government astronomer for New South Wales but refused it.
He continued the publication of these records at intervals for more than 30 years. He had also begun a long series of papers which were published in the Monthly Notices of the Royal Astronomical Society of London, in the Astronomical Register, London, and in the Journal and Proceedings of the Royal Society of New South Wales. He contributed to other scientific journals, and made an immense number of contributions to the Australian press.
In 1872 a equatorial refracting scope was purchased for the observatory, in 1881 Tebbutt discovered another great comet, and in 1886 a new telescope of aperture and focal length was purchased, which enabled him to considerably extend his operations. He published in 1887 History and Description of Mr Tebbutt's Observatory, and followed this with a yearly Report for about 15 years.
A branch of the British Astronomical Society was established at Sydney in 1895 and Tebbutt was elected its first president. In 1904 in his seventieth year he discontinued systematic work, though he retained his interest in astronomy and continued to do some observing, and in the following year the Royal Astronomical Society of London recognised his work by awarding him the Jackson-Gwilt Medal of the society.
In 1908, Tebbutt published his Astronomical Memoirs, giving an account of his 54 years' work, and he was much gratified in 1914, during the visit of the British association, by a visit to his observatory of a small party of astronomers. He died at Windsor on November 29, 1916.
He was commemorated on the reverse side of the Australian $100 dollar bill.