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This instrument is a tall precision chronometer resembling a grandfather clock. The case is wood with a glass front door hinged on the right and closed by two locks on the left side. Two metal strip brackets with holes at the top are affixed to the rear of the case so it can be hung on the wall. There are two small holes in the left side of the case; these have round-topped screws fitted through them to the interior.

Inside the case, the clock instrument consists of a large silver-white coloured metal face with a main dial with a single large central hand in the centre of it. This dial is labelled 0-60. There are two smaller dials on the inside of the larger dial. The upper one is labelled in tens 0 to 50, the lower one measures hours and is labelled in threes, from 0 to 21. Each of these has a single central hand. There is a small round hole on the face with a square peg-end visible through it. The clock mechanism is located behind the face.

Hanging from the mechanism is a pendulum consisting of a rigid metal rod with two mottled glass cylindrical containers affixed on either side of the rod by a metal frame. These can be filled with liquid to increase their weight. Beneath the pendulum there is a slightly curved scale labeled from ‘0’ in the centre to “2” on either side. Hanging loosely alongside the rod there is a metal cord attached to a small pulley wheel.

Accession Number: 2012.ast.20

Alternative Name: Astronomical Chronometer

Primary Materials:

Wood, Glass, Metal: Iron Alloy, Metal: Copper Alloy


On a plaque affixed to the rear of the case behind the pendulum: “SIDEREAL TIME”

Dimensions (cm): Height = 149, Width =48.5, Length=25.5


Astronomical chronometers are for the very precise measurement of time, used to located and time the position of celestial bodies.


Good: The case of the instrument is in very good condition, with only very small marks or scratches. There is white or beige paint splattered over the top of the case, and running down the back of the case. The same beige paint covers the tops of the wall brackets.

The face of the instrument is slightly corroded, with some darker patches. The pendulum rod is rusty down its length. There are some white paint (?) marks on edges of the plaque behind the pendulum.

Associated Instruments:


Date of Manufacture: c. 1930s


This instrument was used at the University of Toronto David Dunlap Observatory in Richmond Hill. Upon its closure and sale in 2009, the chronometer was moved to storage at the Department of Astronomy and Astrophysics at the St George Campus. In 2017, the object was moved to a new storage location in the McLennan Physical Laboratories.

Additional Information and References:

Historical Notes: