"The important place which photography has now assumed as a means of promoting astronomical discovery and research, demands some record should be preserved of the instruments, more especially of those used for carrying out the great work which was the outcome of the Congress of the world's astronomers which met at Paris, in 1887." H. C. Russell

In 1887 astronomers from around the world embarked a massive new enterprise; known as the Astrographic Catalogue project it involved photographing and measuring the stars in both hemispheres. Australia was actively involved in the project with observatories in Sydney, Melbourne, and Perth keen to participate in this international project. Each observatory was allocated a zone of the sky and was expected to record it using instruments of a standard pattern.

British institutions preferred to patronize British makers and Howard Grubb of Dublin was requested to construct seven astrographs, including one for Melbourne Observatory. Repsold's instrument was used to measure the photographic plates taken by the Melbourne and Sydney astrographic cameras involved in the 'Mapping the Stars' project. Originally the plates were to be measured at a central plate-measuring facility in Paris but when this failed to materialise Melbourne and Sydney set up a shared facility located in Melbourne.

For the 'Mapping the Stars' project all the photographic plates were coated with a dry gelatine emulsion introduced to Australia around 1883. All of the photographic plates used in the project were of the same size and they were also exposed to a reseau which produced finely ruled lines around five millimetres apart across the surface of the plate. The resulting image, traversed by these very fine lines, could then be used to measure the plates with respect to the lines to determine the placement of the stars.

These measurements were however a 'painstakingly slow affair' and one which required thousands of work hours for the more than 60 years the Australian observatories were involved in the project. Amongst the four measuring machines used at Melbourne two were made by Repsold, the first of which arrived in 1900.

It appears progress on the measuring was slow in Melbourne and by 1915 there was a huge backlog of unmeasured photographs. This eventually led to the transfer of the responsibility for photographic plate measurement from Melbourne to Sydney and one Repsold plate measuring machine was included in the transfer.

It was not however used for measuring photographic plates taken at Sydney Observatory. This measuring machine was transferred to the Powerhouse Museum along with the Sydney Observatory instruments in 1982.

This instrument remains of national significance due to its pioneering role in Australian science and its association with Australia's earliest astronomers. It is also significant for its association with early nineteenth century astronomical instruments and their makers.

Geofff Barker, Assistant Curator, Total Asset Management Project, February 2008

References
Haynes, Raymond, Haynes, Roslynn, Malin, David, McGee, Richard, Explorers of the Southern Sky, Cambridge University Press, 1996
Glass, I. S., Victorian Telescope Makers, the Lives and Letters of Thomas and Howard Grubb, Institute of Physics Publishing, Bristol and Philadelphia, 1997
Fresneau, A., Argyle, R.W., Mirano, G., Messina, s., Potential of Astrographic Plates for Stellar Flare Detection, cited in http://www.journals.uchicago.edu/AJ/journal/issues/v121n1/200282/200282.html, July 2007.
King, H., C., The History of the Telescope, Dover Publications, New York, 1955
Russell, H. C., Description of the Star Camera at The Sydney Observatory, Alfred James Kent, Government Printer, 1923
Ellery, R.L.J., 'Photographic Charting of the Heavens', cited in Proceedings of the Royal Society of Victoria, Volume IV, part 1, Stillwell and Co., Collins Street, Melbourne, 1892
Urban, S., Corbin, T., cited in 'The Astrographic Catalogue; a century of work pays off', Sky and Telescope, June, 1998

The German firm of Repsold and Son was one of the more important instrument making firms of the nineteenth century and was founded by Johann Georg Repsold around 1799. He, along with his two sons Georg (1804-1885) and Adolph (1793-1867), provided mountings for many of the Merz telescopes. In 1848 the Oxford Observatory installed a heliometer (sun telescope) made by Repsold reputed to be one of the best in the world at the time.

David Gill a pioneer in the art of stellar photography used a Merz heliometer telescope with mechanical parts made by Repsold in 1877 at Ascension Island and later at the Cape of Good Hope. This fact may have had some bearing on why Repsold's was contracted to make telescopes for Potsdam and Berlin which were also used in the Mapping the Stars project.

After over 100 years service the firm of Repsold and Sons was finally wound up in 1919

Geofff Barker, Assistant Curator, Total Asset Management Project, February 2008

References
Glass, I. S., Victorian Telescope Makers; the Lives and Letters of Thomas and Howard Grubb, Institute of Physics Publishing, Bristol and Philadelphia, 1997
King, H., C., The History of the Telescope, Dover Publications, New York, 1955

The plate measuring machine was used at the Melbourne Observatory and the Sydney Observatory. It was used to measure the Melbourne Astrographic Catalogue plates.

Optical instrument, for measurement of astronomical photograph plates, metal / glass / wood / plastic, used at Melbourne Observatory and Sydney Observatory, made by Repsold and Son, Hamburg, Germany, 1900-1902.

An optical machine for measuring astronomical photographic plates. The plate measuring machine consists of a circular metal base on three legs that has been painted black. Attached to the circular base are two adjustable scaled frames into which photographic plates can be inserted. Attached beneath the base is a mirror. The mirror reflects light through a lens fixed into a circular hole in the centre of the base. A tripod, attached over the base, supports a micrometer and eyepiece. Accompanying the machine is a wooden stand. The stand has a circular hole in one side to fit the circular base of the plate machine. Also with the machine are two metal butterfly clips, an electrical lamp made from a tin, an illuminator with various components, four weights and additional components and attachments for the plate measuring machine.

Made: A Repsold & Sohne; Hamburg, Germany; 1900 - 1902


Used: Melbourne Observatory; Melbourne, Victoria

Used: Melbourne Observatory; Sydney

Owned: Sydney Observatory;

H10066

1900 - 1902