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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.

Inside the case, the clock instrument consists of a large white 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. Arranged loose in the base of the case there are a number of small components such as screws and handles.

Accession Number: 2012.ast.19

Alternative Name: Astronomical Chronometer

Primary Materials:

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


On a plaque affixed to the interior rear of the case: “”MEAN TIME-EASTERN STANDARD, Hours numbered from 1 to 24 beginning at [<s>noon</s>] midnight” [‘Midnight’ has been handwritten in pencil.

In white paint (?) on metal top of glass container: “EST”

Dimensions (cm):

Height = 148, 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 wooden case of the clock is in very good condition, with some small marks on the surface. There is beige or white paint splattered over the top of the case; paint has also run down the back of the case. At the top left of the glass front panel there is a small protrusion mark, possibly a chip or original inclusion in the glass. The metal brackets at the rear are somewhat warped and stained with beige paint.

The face is in good condition, with some marks and staining on the white surface, particularly around the rim where some of the numbers appear to have been smudged. The wooden interior is in very good condition, although the scale beneath the pendulum is slightly corroded around the engraved scale and numbering. There are some white paint (?) marks on the edges of the plaque affixed behind the pendulum.

The components in the base of the case are of unknown use. One of the keys may be the key for the clock. There is no liquid in the weights.

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:

This chronometer appears briefly, alongside others, in the short documentary Universe by director Roman Kroitor and Colin Lon, which was filmed at the David Dunlap Observatory in 1960 and featured Professor Don MacRae operating the 74” telescope. Although in the film the chronometers appear to be wall-mounted and operating, Professor Emeritus John Percy has suggested that they weren’t actively in use in 1960 by astronomers, but instead used as evocative props:
“… I don’t remember the film as to whether these were shown in the basement or actually moved up to be filmed. But in those days they [the clocks] weren’t being used for scientific purposes; by then you had an electric clock that was in the dome. But the thing is that these are so visually stunning that I can imagine that any filmmaker would want to use these simply to represent time.”
John Percy was interviewed on March 11, 2021.

Historical Notes: