He was born in Westminster, London. He was the only son of Joseph Smyth and Georgina Caroline Pitt Pilkington, granddaughter of the Irish writer and protégéé of Jonathan Swift, Laetitia Pilkington. His father was a colonial American who lived in East Jersey. He was an English loyalist, however, and after the American Revolution emigrated to England where his son was born.
Having completed his observations, Smyth retired to Cardiff in 1839. His observatory was dismantled and the telescope was sold to Dr. John Lee and re-erected in a new observatory of his own design at Hartwell House. Smyth still had the opportunity to use it since his residence at St. John's Lodge in Stone was not far from its new location, and did a large number of additional astronomical observations from 1839 to 1859. The telescope is presently in the Science Museum, London.
Smyth suffered a heart attack in early September, 1865, and at first seemed to recover. On September 8 he showed the planet Jupiter to his young grandson, Arthur Smyth Flower, through a telescope. A few hours later in the early morning of September 9, at age 78, he died. He was buried in the churchyard at Stone near Aylesbury.
