Astonomy in Sydney predates Sydney Observatory by some 70 years. Lt William Dawes arrived with the First Fleet and set up an observatory at a place now called Dawes Point at the foot of the present Observatory Hill. His instructions were to observe a comet predicted by the famous astronomer, Edmund Halley, to return about 1790.

Although transient decreases in cosmic ray intensity of the type first reported by Forbush (1937) have been observed and studied for more than 40 years using a variety of detectors at many locations, from medium depths underground to those on spacecraft far from Earth, the precise nature of the physical process causing these events is not yet clear (see, for example, McKibben 1981).

Six solar proton events have been observed by ground level cosmic ray detectors so far during solar cycle 21, a little less than one per year. All of these have been much smaller than the giant events observed in solar cycle 19. As with many other aspects of solar activity, the reason for the differences from cycle to cycle remain unknown.

Australian astronomers have a proud history of comet-discovery, beginning with Rumker of Parramatta Observatory in 1824 (Baracchi 1914), and culminating with the outstanding achievements of Bill Bradfield of Adelaide. In the intervening one hundred and fifty years there have been a number of other notable comet-hunters and comet-observers, the most successful being John Tebbutt (see Orchiston 1981, 1982a, 1982b), Walter Gale, David Ross, and J. F. Skjellerup. Comets discovered by these Australian astronomers, and others, are listed in Marsden’s 1982 Catalogue of Cometary Orbits.

Bursts of gamma rays lasting from a fraction of a second to several seconds have been observed by spacecraft since 1967 (Klebesadel et at. 1973). Events with fluxes in excess of 10−4 erg cm−2 s−1 are seen at the rate of several per year for gamma ray detectors with an energy threshold of ˜50 keV. The sources of these bursts remain unidentified and the mechanism(s) responsible for the production of the gamma rays remain(s) in the realm of conjecture. (For a review see Ramaty and Lingenfelter 1982).

Mount Stromlo Observatory came into being on 1 January 1924. First known as the Commonwealth Solar Observatory, it was founded primarily for studying the Sun and solar-terrestrial relations, though from the outset it was much concerned with various aspects of geophysics. There was also a stellar programme, but after a promising start this had to be discontinued. The solar-geophysical regime continued, with success, until World War II. The Observatory went through the War with a new director, and at the end of it embarked on a new and unfamiliar course to develop into the fully-fledged astrophysical institute it has become today. This transition marks an important chapter in the history of Australian astronomy: I have tried here to describe some of its aspects, as they seemed to me.

The Lands Department Building in Sydney is situated on the block bounded by Bridge Street, Gresham Street, Bent Street and Loftus Street. The northern (Bridge Street) end is surmounted by a small copper dome.