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The Australian National Time Service at Mount Stromlo Observatory engages in pure research and sends out time signals which are used for the correction of clocks and as a frequency standard for the determination of exact locations in geodetic and cartographic work, as well as for southern ocean navigation. The Time Service researches, primarily, into problems connected with the motions of the earth and their seasonal and occasional determination. The Photographic Zenith Tube (PZT) is an instrument that checks the time by astronomical means, recording the passages of stars close to the zenith. The PZT was brought into regular use at the Mount Stromlo Observatory from March/April 1957. The last plate observed was on 27 August 1985. The records in this series comprise PZT observing data, Positional Astronomy (National Time Service) day books, minutes of meetings, correspondence, subject files, as well as photographs, diagrams and drawings.

Identified are: possible 60-inch site, Oddie Dome, 74-inch Dome, 26-inch Refractor, Uppsala Schmidt, 50-inch Dome, PZT, 30-inch Reynolds, Schmeidler Hut.

2 x CD-ROM. Content: photographs, measurements, reductions reports, summary files and ancillary notes, together with 'Technical Report 15 Photographic zenith tube observations at Mount Stromlo' by M.J. Miller. Canberra : Division of National Mapping, 1973.

1. Fluctuations in the motion of the pole and the rotation of the earth / paper prepared for the Symposium on Continental Drift, the Motion of the Pole, and the Rotation of the Earth, Stressa, Italy, March 1967. -- 2. Variations in the earth's rotation / paper by H. J. Abraham, circa 1970.

Information on future work of the 26-inch refractor telescope, developments in national time services, implementation of computing and digitisation at observatories, &c.

Topics include effect of a total solar eclipse on the phase of long path VLF transmissions; the Australian height datum; atomic timekeeping and the statistics of general precision signal generators; nationwide precise time and frequency distribution utilising an active code within network television broadcasts, &c.

Catalogues of clocks and descriptions of the Shortt Clock