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H9889 Regulator clock, sidereal-time, wood / metal / glass, made by William Hardy, London, England, 1808-1810, used at the Parramatta and Sydney Observatories, Sydney, New South Wales, Australia, 1821-1980. Click to enlarge.

Sidereal-time regulator clock made by William Hardy

This longcase regulator clock arrived in Australia with Governor Brisbane in late 1821 and was used at Australia's first permanent observatory at Parramatta, New South Wales. Brisbane was a keen amateur astronomer and he brought this clock, along with three others to use as a regulator in conjunction with the observatory's telescopes.

In 1809, the Astronomer Royal, Nevil Maskelyne had ordered an astronomical regulator clock from Hardy to use in conjunction with the new mural circle built for …


Object No.


Object Statement

Regulator clock, sidereal-time, wood / metal / glass, made by William Hardy, London, England, 1808-1810, used at the Parramatta and Sydney Observatories, Sydney, New South Wales, Australia, 1821-1980

Physical Description

The Hardy regulator clocks consists of a timber clock casing and the internal mechanism. The timber case can be split into three main sections, the base, the middle and hood, with the internal mechanism being made up of the movement, clock face and pendulum.

The hollow wooden base is made of a lighter brown wood than the other clock parts. It is a rectangular base with a plain edge on the top and bottom. There is a small hole in the top right hand side. This is not the original clock base, but a modern replacement.

The middle section is made of a dark timber with column fluting, running vertically on the left and right hand side of the central door. The door has a rectangular frame and features a glass panel through which the clocks' pendulum and weights can be viewed. Above the door is the top section, which the hood of the clock slots over to house the movement and dial.

The hood section made of the same dark timber and features an arched top, with column fluting running vertically on each of the two front corners. The centre of the hood has a circular glass window, which can be swung open, through which the clock dial can be viewed. The hood has finely decorated cornice edges and features two circular patterns carved on the left and right sides, imitating small windows.

There are also two small wood screws for securing the movement to the clocks body.
Housed within the clocks body is the movement and pendulum.

The clock movement consists of two main component, the movement or mechanism and the clock face. The movement is made up of a series of brass gears and levers, sandwiched between two brass plates. At the back of the movement there is a small pendulum clip, which the longer pendulum is attached to. The clock face is made of a silver metal and has three main dials. The largest outer dial features numerals '5' through to '60' in increments of five, indicating the minutes, while two smaller dials, one above the other, indicate the seconds and the hours. The clock face has two hands, one for the seconds dial and another for the minutes. The movement is mounted to the top portion of the clocks body, with the hood sliding over the top.

The pendulum is made of brass and metal and comprises three sections. The top features a small rectangular brass clip, used for attaching the pendulum to the back section of the movement, allowing the pendulum to swing. The main body of the pendulum is made from a silver metal and has a small circular hole at the top for clip attachment and a small point at the base for the cage attachment. The final section is the pendulum bob cage and consits of two flat metal sides and a circular brass base for housing the bob. The cage also has a small round nut for fastening the pendulum bob in place.

The pendulum bob is a cylindrical glass tube, which is open at one end. The weight is also cylindrical in shape and consists of a brass casing around grey metal core, possibly lead. The top of the weight has a small hook for attaching to the puylley system while the base has a small dent on one side. The pulley, also made of brass, consists of a single cog, connected to a square clip that the weight can be balance from.


Engraved on the front of the clock face "W.m Hardy London" and "Inv.t et Fecit"



The clock was made by William Hardy in London, England between 1795 and 1821.

Clocks are essential tools for astronomical measurement and their precision defines the accuracy with which the time of a transit can be recorded. In their construction the astronomical clock differs from others mainly in the care with which the parts are produced. For this reason many people regard these clocks as occupying a pre-eminent position in the art of clock making.

There are two main kinds of astronomical clock. One measures the true mean solar time and makes a complete revolution every 24 hours. A common feature of these clocks is the hour hand which revolves only once a day instead of twice as on standard time clocks. The second measures sidereal time which has no direct connection with solar time and instead keeps pace with the apparent movement of the stars and indicates the position of the stars in the sky.

The tilt of the earth on its axis means the earth's orbit is not exactly circular and as a result solar days vary in length throughout the year. To avoid this complication astronomers calculate the time of days by the passage of stars. To do this they measure the time between two successive transits of a star across the meridian. This is known as sidereal time.

Astronomical clocks were made to beat exact seconds of time which depended on the length of the pendulum. The exact length of a pendulum which calculates true seconds was formulated by Huygens at an amount approximating to 39 inches. However this length is slightly different at different parts of the globe and the pendulums themselves can expand or contract depending on the temperature. To overcome this compensated pendulums such as the one invented by the clock maker Graham contained mercury which expanded and contracted to keep the clock beating exact time.

In 1675 the first Astronomer Royal at the Greenwich Observatory, John Flamsteed, commissioned Thomas Tompion to build two clocks. These were wound once a year and had 13 foot pendulums and are thought to be the first year movements ever made. The pursuit of greater accuracy led to many improvements in astronomical clocks and in some cases, such as Clement's anchor escapement, their innovations were incorporated into other timekeeping devices.

In the early nineteenth century there was a great increase demand for astronomical clocks among private and government institutions in Britain. William Hardy, along with Robert Pennington and John Roger Arnold, was one of best known and respected makers of astronomical clocks in this period. His major innovations included the detached clock escapement and a clock balance.

Howse, D., Greenwich Time; the discovery of the longitude, Oxford University Press, 1980
Lloyd, H.A., 'Timekeeping Mechanisms and Clocks for Scientific Purposes', in the catalogue of the British Clock makers Heritage Exhibition, Science Museum, London, 1952
Peck, W., A Popular Handbook and Atlas of Astronomy, Gall and Inglis, London, 1890
Wood, C., 'Robert Molyneux's Astronomical Clocks and Chronometers', in Antiquarian Horology, Number 4, Volume 9, September 1975
Wood, C., 'What's Wrong with Hardy's Escapement?', in Antiquarian Horology, Number 8, Volume 9, September 1976



The clock was one of four brought to Australia by Governor Brisbane in 1821, for use at the Parramatta Observatory and Sydney Observatories

Observatory Stock Number 29


Credit Line

Sydney Observatory Collection, 1983

Acquisition Date

2 June 1983

Cite this Object


Sidereal-time regulator clock made by William Hardy 2022, Museum of Applied Arts & Sciences, accessed 9 February 2023, <>


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