William Hardy transit clock

Essential information

Opening times: 
Royal Observatory, Meridian Line and Historic Royal Observatory, Flamsteed House

Clock this special time-keeper designed to keep astronomers on time when star hunting.

A transit telescope can't be moved to the east and west. The astronomer must wait for the stars in the night sky to move over the telescope. The astronomer records the angle of the telescope and - crucially - what time the star passes through the crosshairs. An accurate astronomical clock is therefore as vital as the telescope itself.

Astronomer Royal, Dr Nevil Maskelyne (1732-1811), recommended that the board of ordnance commission William Hardy to manufacture an exceptional astronomical regulator to accompany Troughton’s ten-foot transit instrument (the mural circle) which was already being constructed. Hardy set to making the regulator with great enthusiasm sparing no expense or effort.

Dr Maskelyne died before the clock was delivered to the Royal Observatory and his successor, John Pond (1767-1836), questioned the £325 bill referring it to the Royal Society for scrutiny. In the end Hardy accepted payment of £200 but the prestige in making such an important timekeeper led to further commissions.

The Hardy transit clock continued to be used for observations until the observatory was relocated in Herstmonceux in 1957.

The half-second and minute galvanic impulses were recorded on a drum chronograph to meter the astronomer’s observations recorded by a hand-held push button.

The twelve inch circular painted dial is signed “Willm. Hardy Inv. et Fecit, New Dead-Beat escapement by Dent”. The outer minute track having arabic five-minute markers enclosing a seconds subsidiary dial with observatory marks and shuttered viewing aperture for the electrical contacts over a twenty four-hour subsidiary.