The J. A. Hamilton Papers at Armagh Observatory consist of his letters and treatises on his observations recorded at the Observatory in Armagh. A number of the letters are from Neville Maskelyne, the Astronomer Royal for England. Maskelyne wrote detailing the requirements for a modern observatory and offered to vet and purchase equipment in London. Hamilton corresponded with other key figures in astronomy at that time, namely J Troughton, Earnshaw, Brinkley at Dunsink Observatory and the Board of Longitude. The letters are concerned with various astronomical observations which he recorded. Some of the letters make reference to events taking place at the time - the firing of canon in Dublin at night (1805) and the Napoleonic Wars (1814). Included in the collection are manuscripts and notes to the Royal Irish Academy, discussing theories and methods of measurement.
Material relating to first instruments used, and measurements recorded at Armagh Observatory.
Itemised list at: http://star.arm.ac.uk/history/archives.html.