The Conservation staff undertook the initial sorting out of the various telescope parts at the Castle Hill store. Earlier in the year, Tim Morris, a metals and engineering conservator at MAAS, had begun the restoration of the Astrograph. He was greatly assisted by a team of enthusiastic volunteers : John Cooper, Jim Poole and Merve Collins,(pictured with Tim above). The first job was to separate the components from each telescope, then re-assemble the Astrograph telescope. Once assembled it could be worked out what parts were missing. and what condition the telescope was in.
The major central shaft had snapped so it was sent to Ainsworth Engineering in Goulburn to be re-welded and reinforced as this is the central pivot the telescope swings from. Research was then undertaken, using the FTIR (Fourier Transform Infrared Spectroscopy) to ascertain the composition of the various paint layers. Scant traces of original paint (black) can be seen around the edges of some of the components but very little of it remains.
The incorrect, blue, top layer of paint with the 1944 khaki paint exposed underneath. The decision was made to remove the incorrect, sprayed, blue paint and restore it to the 1944 khaki colour.
Removing the blue paint by sand blasting with sand or plastic beads was not considered a suitable treatment as this would have damaged the original tin plate covering. A commercial paint stripper was used along with physically paring away the paint with scrapers. This was a slow and laborious process.
Using paint stripper and scrapers, the blue paint is removed to reveal the original tin plate
The Astrograph had to be re-assembled again to check it fitted into the new purpose built East Dome which is currently being reconstructed at Sydney Observatory. It was then disassembled so that the components could be painted.
The image above shows the reconstructed telescope to ensure it will fit into the new dome
The image above shows the undercoat and top coat being applied by brush. The original paint would have been applied with brush, so three coats of zinc based undercoat was applied to each external component. Each coat was sanded afterwards to smooth the brush-strokes. The two top coats, also brushed on, were a two part polyurethane paint that had good brush-stroke qualities. The paint protects the metal from absorbing moisture.
The restoration process has been thoroughly documented and photographed. The telescope is now in place in the East Dome and will be able to be viewed early 2015.
The Astrograph and the 20,000 glass plate negatives that were produced for the Astrographic Catalogue and subsequent projects play a significant role in the development of astronomy. It will be exciting to view these objects, as well as the measuring machine in the new East Dome at Sydney Observatory soon in 2015.
Written By Kate Chidlow, Conservator