The Great Melbourne Telescope was a revolutionary telescope design, and a triumph of mid-19th century engineering. Prior to the GMT, the large reflecting telescopes of astronomers such as William Herschel and Lord Rosse were unwieldy beasts, requiring manual handling and tracking by teams of labourers.

Thomas Grubb devised an equatorial mount for the telescope that required just one assistant in addition to the observer. The GMT also incorporated a mirror support system that could substantially control flexure of the massive mirror – this idea had been devised by Grubb for use on Rosse’s Leviathan. Rather than having the observer placed dangerously at the top of the tube, the GMT eyepiece conveniently remained in the vicinity of standing eye height.

Many of these features would influence telescope design for the remainder of the century and beyond. But the GMT had its limitations, and the speculum metal mirrors were a constant headache to the observers and maintainers.

The GMT was used primarily for the systematic revision of the southern nebulae, comparing observations with the GMT with those undertaken by John Herschel in the 1830s at the Cape of Good Hope. The observations suggested that some significant changes had taken place, but it was difficult for astronomers to be sure if the apparent changes were real or a function of different instruments and observers.

The GMT was also used for photography and spectroscopy. It allowed the first observation of the spectrum of an extragalactic nebula. Its photographs of the moon were some of the finest taken in world in the 1870s, and its photos of nebulae the first taken in the southern hemisphere.

Its greatest astronomical achievements awaited its removal to Mount Stromlo Observatory in the 1940s and rebuilding with a modern mirror in the late 1950s.

  • Lithograph of drawings of the southern nebulae undertaken with the Great Melbourne Telescope, 1885.
    Source: Museum Victoria