This reflector was originally built for the Melbourne Observatory in 1868 for visual (look and sketch) observations. Rather than glass, it had a mirror made of speculum (a heavy alloy of copper and tin) that made the telescope cumbersome to balance. Also, it was used without a dome, exposing the telescope to vibrations from the wind. These problems rendered the reflector inadequate for photography, and from 1893 the telescope sat unused. Mount Stromlo purchased the telescope when Melbourne Observatory closed in 1944. With some significant modifications it became one of Stromlo’s most productive telescopes.
In the 1990s the reflector joined the MACHO project to investigate one of the big mysteries of the universe – ‘dark matter’. Observations of distant galaxies had demonstrated the gravitational presence of an invisible matter that neither emitted nor absorbed light. The Great Melbourne Telescope was used to test a theory that the missing mass is attributed to ‘Massive Astrophysical Compact Halo Objects’ (MACHOs), such as black holes or neutron stars. Over the course of five years, the astronomers observed less than 20 occurrences of this event outside our own galaxy, ruling out MACHOs as primary contributors to dark matter. The composition of dark matter remains one of the Universe’s big unanswered questions.
Just before its destruction in the 2003 bushfire, The Great Melbourne Telescope had been automated to generate a digital map of the southern skies – the ‘Skymapper’ project has since been transferred to Siding Spring Observatory.