In 1874, after two years of enquires, the New South Wales Government Astronomer H C Russell acquired a number of new instruments in preparation for the upcoming Transit of Venus. One of these was a new 11.4 inch telescope (H9886) purchased for the observation of double stars from the optician and instrument maker, Hugo Schroeder.
In 1870 he had made an objective for the Hamburg Observatory and the success of this instrument may have been one reason Russell sought him out. As well as the telescope Russell purchased some additional instruments from Schroeder for use with the telescope. These were a solar polarising eyepiece (H10380) designed for viewing the sun, some eyepieces (H10294), and this filar micrometer mounted on a graduated circuit. A sun diagonal (H10295) used in conjunction with the Schroeder telescope was purchased separately.
This micrometer was primarily used for measuring double star positions. It was still in use in the 1940s when it was worked on by the local instrument maker E Esdaile who replaced the original micrometer.
Haynes, Raymond, Haynes, Roslynn, Malin, David, McGee, Richard, Explorers of the Southern Sky, Cambridge University Press, 1996
Russell, H., C., "Report of Astronomer for 1874 & 1875', New South Wales Government Printer, 1876
Geoff Barker, August, 2007