Great Melbourne Telescope

20 November, 2011

The Great Melbourne Telescope, 1868.
The Great Melbourne Telescope, 1868.
Image: Thomas Grubb (Engraver)
Source: Museum Victoria

Question: What was the Great Melbourne Telescope originally used for?

Answer: The Great Melbourne Telescope (GMT) was built by Thomas Grubb of Dublin in 1868 and erected at the Melbourne Observatory in 1869. At the time it was the largest telescope in the southern hemisphere and the second largest in the world.

It was used to make detailed observations of the southern hemisphere sky, particularly of the southern nebulae. The astronomers primarily made pencil sketches, but in 1883 the GMT was used to take the first experimental photos of southern nebulae.

Photos of the Moon were much easier to take. In 1872, a photo of the moon taken through the GMT was so exceptional that it was immediately sent to astronomers in Britain. The photo was proudly displayed by the Royal Astronomical Society in London, and copies were distributed to all Victoria's schools and libraries.

The Melbourne Observatory opened its doors to the public when the moon was full (and conditions for astronomical observation of nebulae were poor). It became a popular pastime in the colony to gaze through the GMT at celestial objects; even the Governor would bring dinner guests across from the adjacent Government House.

The GMT added great prestige to the growing city of Melbourne. It was a symbol of great wealth, as well as of scientific and intellectual advancement.

The telescope was rarely used after 1890, as new observing techniques and research priorities superseded the telescope. Trying to maintain its speculum metal mirrors in good condition was increasingly difficult.

In 1944 it was relocated to Canberra's Mt Stromlo Observatory and modernised in the 1960s and again in the 1990s. Astronomers at Stromlo undertook significant research with the GMT, including finding evidence of dark matter. The modernised telescope was severely damaged by the 2003 Canberra bushfires.

Fortunately more than 90% of the original telescope has survived and it is now being restored for public and educational viewing.

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