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H10140 Optical instrument, for measurement of astronomical photograph plates, metal / glass / wood, designed by H H Turner, made by Troughton and Simms, London, England, 1892-1915, used by Sydney Observatory, Sydney, New South Wales, Australia. Click to enlarge.

Optical instrument for measurement of astronomical photograph plates

Made by Troughton & Simms in London, Greater London, England, United Kingdom, Europe, 1892-1915.
In 1887 astronomers from around the world embarked a massive new enterprise; known as the Carte du Ciel (Mapping the Stars) project it involved photographing and measuring the stars in both hemispheres. Australia was actively involved in 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.

This instrument was used in conjunction with the photographic plates taken with the astrographic cameras supplied for 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. By 1915 there was a huge backlog of unmeasured photographs and The Sydney Observatory purchased their own plate measuring machines to try to clear the backlog.

Although made by Troughton and Simms this machine was based on an innovative design by Professor H.H. Turner. Turner found that the screw system initially used to measure plates was very labour intensive and instead devised an eyepiece scale measuring machine. This reduced the time taken to measure the stars on each photographic plate.

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, July 2007.

Geoff Barker, August, 2007


Object No.


Object Statement

Optical instrument, for measurement of astronomical photograph plates, metal / glass / wood, designed by H H Turner, made by Troughton and Simms, London, England, 1892-1915, used by Sydney Observatory, Sydney, New South Wales, Australia

Physical Description

Optical instrument, for measurement of astronomical photograph plates, metal / glass / wood, used at Sydney Observatory, designed by H H Turner, made by Troughton and Simms, London, England, 1892-1915

An optical machine for measuring astronomical photographic plates with a wooden storage box and a cylindrical weight. There are three metal attachments with the machine and a white glass plate. The machine allows astronomical photographic plates to be measured in two co-ordinates at right angles to each other. Measurements are made using reseau lines marked on a glass graticule.

Observatory stock number 292, 1920.



The instrument was made by Troughton and Simms Limited in London, England between 1892 and 1915.

In 1782 John Troughton purchased Benjamin Cole's shop in Fleet Street, London enabling him to sell his own signed products. His instrument making business supported several dynasties of Troughton's before becoming Troughton and Simms and later still Cooke Troughton & Simms. This firm was one of the most well respected firms of instrument makers of the 1800s.

While his brother enjoyed some early success the business really expanded once Edward Troughton (1756-1835) took over the business in 1807. Edward and his brother John were both designers and manufacturers of instruments and the quality of their work won them contracts with the leading Government bodies of the time. These included The Royal Society, the Greenwich Royal observatory, the Board of Longitude, the Board of Ordinance and the East India Company.

One of the main factors in the success of the business was the use of a dividing engine which could speed up the labourious process of marking the small divisions of measurement necessary for scientific instruments. This machine was based on that designed by Jesse Ramsden (1735-1800) which had won a prize from the British Board of Longitude in 1775. As a result of this the Board of Longitude was allowed to instruct Ramsden to allow up to ten other instrument makers to copy his machine. One of these was John Troughton and the new machines established both Ramsden's and Troughton's reputations. The dividing engine speeded up both accuracy and production and rather than spending 12 weeks, six days a week and eight hours a day graduating two meridian circles this machine enabled the same job to be completed in around 10 hours.

The workshop produced a broad range of instruments from large telescopes and theodolites through to smaller mathematical instruments. Before 1835 most of the optics appear to have been supplied by Dollond as Edward Troughton was reputed to be colour blind. It is also important to note that from the early years the precision engineering of castings and turnings of their instruments were mainly outsourced to Maudslay Field & Donkin or Ransome's & May.

One of Edward Troughton's apprentices William Simms was taken into partnership in 1826 and after Edward died in 1835 Simms became the manager of the establishment and company became Troughton & Simms. Under Simms the company continued to expand and produced instruments for Britain and her colonies as well as for markets in Europe and America. When William Simms died in 1860 the estate was worth around £80,000. The company was next managed by William Simms (junior) and his cousin James who carried the firm into the industrial age.

The 1860s they moved the company from Fleet St to two acres of land at Charlton on Woolwich Road and by1866 the factory employed 61 men and 20 boys. For the 1874 transit Troughton & Simms made only five transits and four portable azimuths but did refurbish some older telescopes lent for the occasion. Telescopes and transits of the period they were often hybrids with the structure ordered from Grubb's or Troughton & Simms with lenses from Cooke.

However by 1887 the company was able to produce all the parts necessary for their instrument and the company employed nearly 200 people. James Simms died in 1915 and the company was turned into a limited liability company by his two sons William and James. Things however were not so easy for the two sons and in 1922 the business was brought out by their rival T. Cooke & Sons becoming Cooke, Troughton & Simms.

Todd, David, P., Stars and Telescopes, Sampson Low, Marston, and Co., 1900
Chaldecott, J., 'Printed Ephemera of Some Nineteenth Century Instrument Makers', in Blondel, C., Parot, F., Turner, A., Williams, M., (eds), Studies in the History of Scientific Instruments, Rogers Turner Books, London, 1989
King, H., C., The History of the Telescope, Dover Publications, New York, 1955
McConnell, A., Instrument Makers to the World; a History of Cooke, Troughton and Simms, William Sessions, York, England, 1992



The plate measuring machine was owned by and used at the Sydney Observatory, Watson Road, Observatory Hill, Sydney, New South Wales, Australia.


Credit Line

Ex Sydney Observatory, 1984

Acquisition Date

24 January 1984

Cite this Object


Optical instrument for measurement of astronomical photograph plates 2020, Museum of Applied Arts & Sciences, accessed 11 July 2020, <>


{{cite web |url= |title=Optical instrument for measurement of astronomical photograph plates |author=Museum of Applied Arts & Sciences |access-date=11 July 2020 |publisher=Museum of Applied Arts & Sciences, Australia}}

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