The baseline of East-West array of the Fleurs Synthesis Telescope (FST) has been extended from 786 metres to 1585 metres by the addition of two 13.7 metre dishes. A digital receiver has been built to accommodate the extra delay and correlation requirements, low noise FET preamplifiers have been installed on the large antennas, and a software package has been developed for processing observation data on a VAX 11/780. The FST is now capable of producing accurate wide field maps at 1415 MHz with a resolution of 20 arc seconds and a sensitivity of several milliJansky.

The four-fold advantage over a conventional 4 m reflector which naive information theory confers on the 1.2 m UK Schmidt telescope (Dawe and Watson 1982, Watson 1983) is only approachable in practice under certain rather specific conditions. These relate principally to the surface distribution on the sky of the object classes of interest, and the type of detection employed. Clearly, for general survey work with sky-limited photographic detection, the information advantage is high, but it can be demonstrated (Dawe and Watson 1983) that the relatively new technique of multi-object fibre-optics spectroscopy (eg Hill et al. 1980, 1982, Gray 1983, Lund and Enard 1983) with linear detectors offers very high potential in certain regimes of operation. In particular, the UK Schmidt telescope (UKST) equipped with 400 fibre channels has four times the effective light grasp (= number of fibres utilized × aperture) of a 4 m reflector (with a 1 deg field and equipped with any number of fibres) for target objects with surface densities between approximately 1 and 10 per square degree (Dawe and Watson 1983). Objects ranging from galactic variable stars to quasars lie within these limits, but of especial interest are galaxies, whose apparent luminosity function in this range of surface densities runs from magnitudes 15 to 17 (MacGillivray, private communication). Large-scale, medium accuracy (60 km s−1) redshift surveys of galaxies within this magnitude range promise to be extremely fruitful (Davis 1982) and are easily within the reach of the UKST fibre-coupled to a CCD spectrograph (Watson and Dawe 1984).

Waves of variation in the daily average cosmic ray intensity at the Earth’s surface were first detected in the neutron monitor record. Following the abnormal cosmic ray storm of September 1978, a sinusoidal 13.5 day periodicity was observed in the average intensity (Pomerantz and Duggal 1979), persisting for at least two solar rotations. Further observations, including underground data from the southern hemisphere, confirmed that not only were the waves isotropic but exhibited approximately a p−1 variational dependence on primary rigidity p (Duggal et al. 1981). No further evidence for this kind of wave has yet come to light. However, in the latter half of 1982 a series of 27-day waves that were apparently of a different character were detected. The evidence for their presence resulted from an analysis of the disturbed period that followed the occurrence of the large Forbush Decrease commencing 13 July 1982. It seemed at first that they could be described as anisotropic waves of the well-known interplanetary North-South asymmetry (Jacklyn and Pomerantz 1983).

Recently, a new branch of astronomy has emerged following the detection of ultra-high energy (UHE) γ-ray emission from Cygnus X-3 by Samorski and Stamm (1983). This discovery was made using the extensive air shower (EAS) array of the University of Kiel, Germany. Such arrays are designed to detect EAS, the cascades of secondary particles (mainly electrons and protons), which are generated in the atmosphere by the interaction of cosmic ray nuclei of energy greater than ˜ 1015 eV. These arrays are also sensitive to EAS initiated by primary γ-rays and, depending on their design, have angular resolutions as good as the SAS-II and COS-B γ-ray telescopes which operated at ˜ 100 MeV energies. At present, there is no effective way to veto proton or nucleus-initiated EAS and so one must look for a significant excess of EAS from within a cone of resolution centred on a suspected source direction.

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.

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.