Spectrographs like astrographs were photographic apparatus attached to telescopes to record the stellar activity. They were similar to the spectroscope except the photographic plate was used instead of the eye-piece.

The spectroscope used prisms to spread stellar images out into lines of spectral wavelengths rather than providing an image of what was seen through the lens of a telescope. The light from stellar objects is passed through a slit and collimator to produce a parallel beam of radiation passed through a prism, or prisms, to disperse it into different wavelengths.

It was an American Henry Draper who successfully introduced the use of the camera to photograph spectra and introduced the spectrograph to the world. His first successful photograph was taken in 1872 and was of the star Lyrae. In 1876 Draper made a piece of apparatus he called a 'spectrograph' which comprised of a "Browning direct-vision prism train and a 7-inch Voightlander portrait lens. Draper conducted numerous experiments on the arrangement of prisms and lens but he died unexpectedly in 1882 before his experiments were finalised.

The work of Draper was carried on by another pioneer stellar photographer Professor Pickering, Director of the Harvard College Observatory. In 1885 Pickering installed an eight inch Voigtlander lens configured by Clarke at Cambridge. He later worked on the Bruce telescope which was able to impress as many as 400,000 stars on a single 14 x 17 inch plate due to the great aperture of the lens combined with a relatively short focal length.

These telescopes have been used for both spectral and point photography but the use of spectroscopes attached to telescopes have afforded the best results for stellar photography allowing many more stars which could not be seen with the naked eye to be measured for the first time by astronomers.

This spectroscope arrived at Sydney around 1915 and was made by the instrument maker Adam Hilger who in 1875 opened up his premises at 192 Tottenham Court Road, London. Although significant for being made by one of the leading instrument makers it is reputed to have been little used during its tenure at the observatory. This was probably through no fault of the instrument which although very sensitive to small changes in focus was still in use as late as 1939. [see associated exercise book (H9955-5 with graphs and notes made using the spectrograph]

References
Todd, David, P., Stars and Telescopes, Sampson Low, Marston, and Co., 1900
Haynes, Raymond, Haynes, Roslynn, Malin, David, McGee, Richard, Explorers of the Southern Sky, Cambridge University Press, 1996
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
McConnell, A., Instrument Makers to the World; a History of Cooke, Troughton and Simms, William Sessions, York, England, 1992

Geoff Barker, August, 2007

Adam Hilger Ltd.
The German born instrument maker Adam Hilger opened up his premises at 192 Tottenham Court Road, London with his brother Otto in 1875. By the end of the nineteenth century Hilger had a well established reputation for the making of high quality optical instruments, especially spectroscopes and rangefinders. In 1916 the rival instrument maker Cooke's purchased 6,000 shares in the firm giving them a six-tenths holding in Adam Hilger Ltd., and most of these were in turn owned by Vickers. In 1926 the combined business reformed as Cooke, Troughton and Simms.

References
De-Clerq, P.R., Nineteenth Century Instruments and their Makers; Rodopi, Amsterdam, 1985
McConnell, A., Instrument Makers to the World; a History of Cooke, Troughton and Simms, William Sessions, York, England, 1992

This stellar spectrograph was used at the Sydney Observatory.

Optical equipment, stellar spectrograph and accessories, brass / glass / wood / paper, used at Sydney Observatory, made by Adam Hilger Limited, London, England 1915.

A spectrograph consisting of a spectroscope (used for examining the spectrum) fitted with a photographic attachment. There is a protective lens cap over the spectroscope slit and a collection of documents relating to the spectrograph. The documents include a blue print, instructions, an exercise book, a delivery slip, an 'Error and Rate' card and an 'Occulation Form'.
Observatory stock number 153.

Made: Adam Hilger Ltd; London, England; 1910 - 1915


Used: Sydney Observatory;

Owned: Sydney Observatory;

H9955

1910 - 1915