A THOUSAND WORDS | FIRST LIGHT & DARK MATTER
BY LIZ CLARKSON
If you are attending a trivia night, here are three questions that only the keenest of star-gazing participants are likely to know.
- Which telescope first mapped the southern hemisphere skies?
- Through which telescope were the first signs of ‘dark matter’ observed?
- Where is the telescope now?
If you answered ‘The Great Melbourne Telescope’ (GMT) you are on the winning team. Currently, the GMT is dismantled in a large restoration area in Melbourne. Every available working part has been identified, numbered, restored or rebuilt… You earn extra points if you know why the GMT is in parts.
Historically, the GMT is the grand dame of Australian astronomy, bought by the Victorian Government for 5,000 pounds in the 1860s. She was constructed in Dublin by Thomas Grubb, world expert in telescope construction of that era. Her ‘first light’ was in 1869, an astronomical term that refers to a telescope’s first viewing to the universe.
The GMT remained in Melbourne until the 1940s and was then sold to the Mt Stromlo Observatory. It was a working telescope until it was severely damaged in January 2003 fires. Afterwards, the GMT had been in the open of Canberra’s extreme temperatures for at least four years when members of the Astronomical Society of Victoria (ASV) considered the possibility of restoration. In 2008, ASV members Barry Cleland, Jim Pollock and Stephen Bentley were the first to assess the viability of restoring the GMT and the restoration proper began in 2009.
All remaining parts of the GMT were returned to Melbourne where the ASV volunteers began their engineering detective work as there were no plans, diagrams or original documentation on the GMT. A dedicated union exists between 15 exceptional ASV volunteers and Museum Victoria. The GMT is a jigsaw with missing pieces and each Wednesday the image becomes a little clearer. The team’s professional backgrounds include geology, journalism, science as well as civil, electronic and mechanical engineering.
“I have been passionate from the start to see it finished” said Barry Cleland. “I love the progress despite the lack of drawings and the missing 180 parts.”
Australia had been colonised less than 100 years when Melbourne achieved the honour of owning the largest operational telescope in the world. The optics on many of the early telescopes were based on a refractor with a lens. The GMT was built with a speculum mirror lens and is the last of the great mirrored telescopes.
An unforgettable moment for the team came in 2010 when a staff member found a box in the museum’s store and called for expert help to confirm the contents. The box contained the original flotation system for the telescope’s one-ton white bronze mirror. It was a joyous day for the GMT reconstruction team who had long wondered what had happened to this magnificent item of 19th century engineering which provides a balanced bed of 48 steel balls to support the back surface of the mirror evenly, keeping distortion of the mirror surface to less than a 1/10,000th millimetre.
Matilda Vaughan has an engineering background and is a Museum Victoria curator, working with the project restoration team. She is enamoured with learning about the construction methods of the 1860s.
“I have been reading many technical books of the period,” said Ms Vaughan. “They used slightly different terms so we are becoming more literate in 1860s process methods. I am also wondering if the steel that was used to make the helical lattice tube was a very early form of Bessemer manufactured steel.”
Barry Clark, a retired defence scientist, has been associated with the Melbourne Observatory since 1954 and has written on the heritage significance of the GMT.
“Dark matter was first identified through the GMT at the Mt Stromlo Observatory in the early 1990s and written up in ‘Nature’ in 1993. Scientists took millions of observations of the brightness of stars over several years.” explains Barry, “Changes in intensity were consistent with dark objects passing between Earth and specific stars. Scientists are still working on understanding not only what dark matter is but also the influence it has on the visible universe.” The research article from the 1993 edition of ‘Nature’ is available at its website at the following link.
“The GMT is a masterpiece of design. It was the epitome of marvelous Melbourne and deserves to be far better known and appreciated by the Victorian public” said Barry. The dollar value of the ASV work is incalculable, unlike the restoration costs. Funding for the project is an ongoing challenge. Three large donors have contributed in the past twelve months but much more is required before the GMT can be fully functioning and the public is welcome to donate. The replacement mirror alone, yet to go out to tender, is likely to be in excess of $200,000.
Many parts of the GMT can be repaired or remade in the restoration area by the combined efforts of Museum Victoria staff and the ASV volunteers. When larger equipment is required, it is manufactured by the staff at Scienceworks.
Every Wednesday the devoted team measure, calculate, discuss and problem solve every millimetre of this beautiful structure. A 2 metre high photograph of the telescope from 1885 is a key reference for the group as they establish which parts are original and which were replaced at Mt Stromlo Observatory. Every bolt, connection or moving part is researched and evaluated with meticulous accuracy.
Discussion about the expected completion date brings gentle smiles of hesitation. The ASV team hope to have the GMT back home at Observatory House in 2019 to coincide with the 150th anniversary of her arrival in Melbourne. Many stars will be shining that night.
Everyone interested in following the progress of the GMT restoration or wanting to donate to this great cause can do so through www.greatmelbournetelescope.org.au The ASV team will appreciate your help in restoring an invaluable piece of Melbourne’s history.
Liz Clarkson is an emerging photographer and contributor to the Northsider, including articles, On the Scene and Melbourne Snap. To see more of Liz’ work you can press here.