Dreyer was born in
Copenhagen. His father, Lieutenant General John Christopher Dreyer, But in 1874, at the age of 22, he went to
Parsonstown,
Ireland. There he worked as the assistant of
Lord Rosse (the son and successor of the
Lord Rosse who built the
Leviathan of Parsonstown telescope). During 1878 he moved to
Dunsink, the site of the Trinity College Observatory of Dublin University to work for
Robert Stawell Ball. In 1882 he relocated again, this time to
Armagh Observatory, where he served as Director until his retirement in 1916. In 1885 he became a British citizen. In 1916 he and his wife Kate moved to
Oxford where Dreyer worked on editing the works of
Tycho Brahe. He won the
Gold Medal of the Royal Astronomical Society in 1916 and served as the society's president from 1923 until 1925. He died on 14 September 1926 in Oxford, where he is buried in
Wolvercote Cemetery. A
crater on the
far side of the Moon is named after him. ==Works==