Great Melbourne Telescope volunteers

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by Kate C
Publish date
13 March 2014
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Each Wednesday, a dozen or so engineering and astronomy buffs head to a museum workshop to restore one of Marvellous Melbourne's grandest marvels. The Great Melbourne Telescope (GMT), scorched by the Mount Stromlo fires in 2003, is being resurrected thanks to an estimated 10,000 hours of volunteer work (so far). This group recently received a Certificate of Appreciation in the 2013 Arts Portfolio Leadership Awards.

GMT restoration team Mathew Churchward reading out the Arts Portfolio Award commendation to the Wednesday restoration workshop team.
Source: Museum Victoria
 

The workdays have "a bit of a men's shed feel about them," says Senior Curator Matthew Churchward. He coordinates the project alongside Curator of Engineering Matilda Vaughan. The combined knowledge in the room – all members of the Astronomical Society of Victoria, many with experience in engineering, electronics, astronomy and optics – means this piece of 19th-century technology is in expert hands.

Three men with computer L-R: Barry Cleland, John Cavedon, new volunteer Norm and Stephen Bentley working on technical drawings of GMT parts.
Source: Museum Victoria

Building telescopes is a common pastime for amateur astronomers; volunteer Barry Adcock has a home-built a 14-inch diameter telescope for his backyard dome observatory, plus another telescope that allows him to view the stars from inside his house. For many, stargazing is a habit they picked up when very young. Scottish-born Jim Pollock recalls a lunar eclipse in 1949 during which the moon was bright blue after forest fires in Canada. "In the atmosphere, tiny particles of pinene, the oil from the pine trees, scattered red light beautifully and just let the blue light through." Another volunteer, Barry Clelland, remembers looking up as a kid from his backyard in the suburbs and thinking, "that's half the universe there. You could see the Milky Way in Heidelberg back then."

On this day, a sub-group is working on the mirror polishing and grinding machine, a beautiful hulking contraption with a cast iron frame and gears and shafts. The GMT's half-ton speculum metal mirrors tarnished over time, so every few years they were removed and reconditioned with this machine. "We're still trying to work out exactly how it was driven," says Matthew. The mirror sits on a rotating table and as it moves, the polishing head also rotates, "so it doesn't get a flat spot in any part of the mirror. It keeps moving as it's rubbing." Or, like "patting your head and rubbing your tummy," jokes volunteer David Linke. The team hopes to have the polishing machine working within the next year as a hint of what's to come with the telescope itself.

David Linke with the mirror polishing machine. David Linke with the mirror polishing machine.
Source: Musuem Victoria
 

In the workshop, parts of GMT are laid out on pallets and benches. With a grin, David says, "it's a big jigsaw puzzle, isn't it?" Above it all, for equal parts reference and reverence, hangs a large-scale historical picture of the GMT in operation.

Museum workshop A view of the workshop with the GMT’s lattice tube in the foreground. On the back wall hangs the large historical photograph of the GMT at the Melbourne Observatory.
Source: Museum Victoria
 

Most of the large parts of the GMT were recovered after the 2003 Mt Stromlo fires. "Oh golly, it was a dirty job to get everything out of that cube," recounts David. "The aluminium had melted from the dome and filled up the screw holes so you couldn't see where things were undone." Many months of work saw the GMT dismantled and its surviving parts audited. Fortunately, the GMT had an unofficial champion in Barry Clark, who has been involved with the Melbourne Observatory since 1955. At that time, decommissioned equipment went into storage and was at risk of being lost. Says Matthew, "Barry's been instrumental in recovering bits and pieces that were hidden under the floor. He's discovered some key bits of equipment that went right back to the very earliest observatory at Williamstown."

Detail of the dismantled cube of the GMT. Detail of the dismantled cube of the GMT.
Source: Museum Victoria
 

Lengthy reverse-engineering is recreating the missing parts. "We go out there with a ruler and pencil and paper, take measurements and sketch it up roughly," says Campbell Johns. The measurements are made in imperial units to match Irish manufacturer Thomas Grubb's original specifications, before conversion to metric for fabrication. Some of the team with technical drawing expertise convert the workshop sketches into digital CAD files. There's a lot of cross-checking with old photographs, drawings and the extant parts.

"We don't even know if there was ever a full set of working drawings," says Matthew. "It appears they did the basic layout and started building it before they had the detailed design. You can see evidence in the way parts were modified during the construction process, like spots flattened out of a casting to make a seat for another component." A volunteer adds, "Pretty amazing given in those days there were no angle grinders or power drills or oxy welders. It was all done with cold chisels."

Three men with computers L-R: Barry Clark, Barry Adcock and Mal Poulton working on optics design specifications for the GMT.
Source: Museum Victoria

So why are these men devoting their spare time to this project? It's evident from the way they talk about the GMT that they admire its history and innovation. In addition to its astronomical achievements, including the first observations of southern nebulae, the ingenious nature of its design bewitches them. It had two axes and counterweights that allowed just one person to move the beautifully balanced telescope. In its lifetime there were larger scopes, but none so nimble. Matthew's view is that it's an opportunity of a lifetime for amateur enthusiasts to build such a large telescope; few individuals would have the resources to do so alone. Other volunteers nominate restoring an important part of Melbourne's history as their prime incentive – they want to see it back in its old home.

Indeed, the end goal is to return the working telescope to the Melbourne Observatory for public viewings. Its original configuration restored, there may be new electronic additions to allow digital photography or remote operation via the web. As Matthew says "It could be very inspiring for astronomy in Victoria."

Links:

The Great Melbourne Telescope website contains the story of the telescope, and updates about its restoration through the ASV's Phoenix newsletter

Follow the GMT project on twitter: @GMT21stC

Great Melbourne Telescope on Collections Online

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Peter Linstead 20 April, 2014 14:30
Congratulations on all your efforts in restoring THE GMT, perhaps if I had known what you were doing I may have been able to help. In 1989 I was presented with the project design to refurbish the GMT for the MACHO project
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