Portable transit telescope, 3.25 inch aperture, 42 inch focus, made by Troughton & Simms, London, circa 1850.

This instrument was transferred from the Victorian Survey Department to Williamstown Observatory in 1854, and was the primary transit instrument used at Williamstown Observatory until an instrument of 5 inch aperture was acquired in 1861. The instrument was used as a portable transit during the Geodetic Survey of Victoria, conducted under the supervision of Government Astronomer Robert Ellery.

In 1867 the instrument was loaned to Charles Todd at the Adelaide Observatory, who used it for measuring the longitude difference between Melbourne and Adelaide Observatories, and for fixing the boundary between South Australia and New South Wales. Todd returned it to the Melbourne Observatory in 1897.

Physical Description

Brass, with level and 2 brass supports.


This telescope is of historical significance because of its close association with the establishment of the Williamstown Observatory, the first government Observatory in Victoria. It was the principal astronomical instrument in the new observatory, where it was used to establish the longitude of Williamstown Observatory and to maintain the time signals with the Williamstown time ball and by telegraph connection to Melbourne. It was subsequently used during the Geodetic Survey of Victoria to help establish the primary survey markers through the colony, facilitating European settlement.

It is of scientific and technological significance for its close association as an early instrument at the Williamstown Observatory and its use by Government Astronomer Robert Ellery.

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