Thomas Maclear was born on 17 March 1794 in Newton Steward, Ireland. He trained to be a medical doctor. He was a keen amateur astronomer and was made a Fellow of the Royal Society of astronomers.
Maclear arrived in South Africa on 5 January 1834 to assume his duties as Royal Astronomer at the Cape. He immediately established an observatory and scheduled astronomical, meteorological and magnetic observations. Between 1834 and 1838 he worked closely with John Herschel, who was carrying out surveys of the southern sky. From 1841 to 1848 he surveyed an area stretching from Namaqualand to Cape Agulhas to redetermine calculations of the size and shape of the earth. This created a sound foundation for a trigonometric survey and accurate mapping of the Cape colony. Some of his beacons are still used by cartographers, such as the Maclear beacon at the highest point on Table Mountain. David Livingstone was a close friend and both had a keen interest in the exploration of Africa. With Maclear’s astronomy observation and assistance, Livingstone was able to plan his expeditions carefully.
Maclear was knighted in 1860 for his achievement as an astronomer and he retired in 1870. He died on 14 July 1879 in Mowbray, Cape Town. The town of Maclear, Eastern Cape and Cape Maclear are named after him.