Chronograph from Melbourne Observatory, designed by Government Astronomer Robert Ellery and built at the observatory workshop in the 1860s or 1870s.

This was one of several chronographs used to record the transits of stars or other heavenly bodies. When the observer on the transit instrument depressed a button to indicate that the star had crossed the transit lines, an electrical impulse to an electronmagnet moved the pen to one side, leaving a mark at the exact time that the star crossed the meridian. The speed of rotation of the drum is accurately controlled by the centrifugal governor.

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