Christie graduated in 1868 from Trinity College Cambridge and in 1870 became Chief Assistant at the Royal Observatory, Greenwich under Airy before replacing Airy in 1881 as Astronomer Royal. Under Christie the Observatory not only continued its work in positional astronomy but also began a programme of stellar photography and one of making daily records of solar activity.
John Jackson came straight from Cambridge University to become Junior Chief Assistant at the Royal Observatory, Greenwich in 1914. In 1933 he moved to South Africa to become the Astronomer Royal at the Royal Observatory at the Cape of Good Hope, succeeding Harold Spencer Jones, who returned to Greenwich to succeed Frank Dyson as the Astronomer Royal. Jackson remained at the Cape until he retired in 1950.