John Jackson's secondary school education was at Paisley Grammar School. At this stage he was not aiming at a university education so, although he took a broad range of science subjects and modern languages, he did not take Latin or Greek one of which was compulsory at this time to enter university. He completed his secondary education in 1903 with chemistry being his best school subject. He now decided that he did want to enter university so spent the summer making good his lack of Latin so that he could sit the entrance examinations of the University of Glasgow. He was clearly successful since he was awarded a small bursary after taking the examinations.
Entering the University of Glasgow, Jackson decided not to specialise in his best school subject of chemistry but instead studied mathematics and physics. He graduated in 1907 with a B.A. with First Class Honours in Mathematics and Natural Philosophy (as physics was called at this time). He continued to study a wide range of science subjects and was awarded a B.Sc. from Glasgow in 1908 with special distinction in mathematics, natural philosophy, astronomy and chemistry. It was astronomy which become his main passion, through outstanding teaching by Ludwig Becker, during his final years at Glasgow and Jackson decided that he wanted to make a career in the subject. There was little chance to progress further in astronomy in Glasgow, so he decided to continue his studies at Cambridge.
He went to Trinity College, Cambridge in 1909 and there he was able to take courses on a wide range of subjects within astronomy, pure mathematics and applied mathematics. In 1914 a vacancy arose at the Royal Observatory in Greenwich for a Junior Chief Assistant and the Astronomer Royal Sir Frank Dyson appointed Jackson to the post. His immediate superior was the Senior Chief Assistant, Spencer Jones. World War I was to force a break in his career, however, and in 1917 he received a commission with the Royal Engineers and was sent to France. There he used his mathematical skills in sound ranging, then in the following year he was assigned to the British Fourth Army to carry out the task of plotting artillery trajectories. He continued in this role until 1919 when he was able to return to his post at the Observatory at Greenwich. His main interests at Greenwich were in double stars (collaborating on this investigation with Herbert Hall Turner, the Savilian Professor of Astronomy at Oxford University), meridian observations and the time service. He also worked on the rotation period of Neptune and was able to produce a figure much closer to the correct value than that accepted at the time. During his time at Greenwich he was promoted to Senior Chief Assistant.
In 1933 Jackson was appointed His Majesty's Astronomer at Cape Observatory, Cape Town, South Africa. The position became vacant since the previous holder Harold Spencer Jones had returned to Greenwich to succeed Frank Dyson as the Astronomer Royal. Jackson, who went out to South Africa with his wife Mary Beatrice Marshall, also became Director of Cape Observatory, and he filled this position until he retired in 1950. The authors of  write that:-
... he was to suffer the staff disruption caused by years of war. In spite of this, his term of office was noted for its production of a mass of valuable work. Jackson's special concern was the stellar parallax programme; he undertook the necessary reductions and observations personally, at a time when two thirds of his staff were "up north". Jackson retired in 1950, having measured the distances of over 1600 southern stars with greatly improved accuracy and having advanced or completed all the major projects which had been going on at the time of his appointment.There was a total eclipse of the sun in South Africa on 1 October 1940. Plans had been made to send a team from Greenwich to observe this but World War II prevented this from going ahead. Jackson was thus left in charge of the observations for this important event. Taking equipment sent out from London, Jackson headed a party from the Cape Observatory to the site chosen for observations.
After he retired in 1950, Jackson returned to England living in Ewell, Surrey. He received many honours for his contributions. These included a CBE in 1950, the Royal Medal from the Royal Astronomical Society in 1952 and the Gill Medal of the Astronomical Society of South Africa in 1958. He was president of the Royal Astronomical Society from 1953 to 1955 and during this time he went to Stromatad in Sweden to observe the total eclipse of the sun on 30 June 1954. During the last few years of his life he suffered from ill health and died following a short illness.
Article by: J J O'Connor and E F Robertson