In 1774 Provost Francis Andrews bequeathed £3,000 to establish the Andrews Professor of Astronomy and to build an observatory at Dunsink. From 1792 until 1921, the Andrews Professor carried the title Royal Astronomer of Ireland, a title that was established by the Letters Patent of King George III. According to the Statutes of the College, the Andrews Professor was required to "make regular observations of the heavenly bodies ... and of the sun, moon and planets".
Probably the most famous scientist to hold the Andrews Professorship was Sir. William Rowan Hamilton who was apointed at the tender age of 21! His apointment was not without controvercy as Hamilton paid little attention to his official "observational" duties, instead focussing on his research on more theoretical problems in physics, such as conical refraction, quaternions, and mechanics.
The Andrews Professorship and Dunsink Observatory were abandoned by Trinity in 1921, but the Observatory was taken over by the Dublin Institute for Advanced Studies in 1947. The Royal Astronomer title lapsed in 1966 when TCD adopted new statutes. The Andrews Chair was re-established as an honorary chair at Trinity in 1984. An excellent description of the history of the Andrews Professors of Astronomy by Prof. P. A. Wayman can be found in The Irish Astronomical Journal.