In 1860 Reverend William Scott, the first astronomer appointed to the new Sydney Observatory, ordered a new 7 1/4 inch refracting telescope. Arriving in June 1861 it was made by the German firm of Georg Merz & Sons (1793-1867). This lens also made by Merz & Sons was used in conjunction the Merz telescope. Like many of the instruments ordered by the observatory this telescope and lens were not without problems but overall they appear to have been a good purchase.
In 1870 the then Government Astronomer H. C. Russell found problems with the lens while using the instrument for double star measures. As a result he adjusted the lenses by separating them with thin pieces of tin and "after many attempts, I found the definition wonderfully improved." The lens has a focal length of 315cm (10 feet 4 inches).
This seems to have improved the usefulness of the telescope and in 1871 Russell used it to make observations on the positions of stars in the Nebula about Argus. In 1872 he was using it to look at the coloured cluster of stars around Kappa Crucis which had previously been looked at by Sir Thomas Brisbane's 2-inch mural circle. In 1874 the Merz telescope went to Eden with W. Scott to observe the Transit of Venus.
By 1878 the worth of this instrument was no longer in doubt as illustrated by the following comments by H. C. Russell, "Of the quality of the 7 1/4 -inch telescope I need say nothing more now than it is a first-class instrument " From 1890 to 1947 it was used as the guide telescope for the Sydney astrographic telescope. It is clear from the continued use of this telescope and the lens that it was an integral part of the Observatory's operations and played a significant role in the early development of astronomy in Australia.
Todd, David, P., Stars and Telescopes, Sampson Low, Marston, and Co., 1900
Russell, H., C., Nebula About Argus, cited in 'Scientific Papers 1871 to 1879', New South Wales Government Printer, 1879
Russell, H., C., The Coloured Cluster About Kappa Crucis, cited in 'Scientific Papers 1871 to 1879', New South Wales Government Printer, 1879
Haynes, Raymond, Haynes, Roslynn, Malin, David, McGee, Richard, Explorers of the Southern Sky, Cambridge University Press, 1996
De-Clerq, P.R., Nineteenth Century Instruments and their Makers; Rodopi, Amsterdam, 1985
Geoff Barker, August, 2007