The grating ring response of the Molonglo Observatory Synthesis Telescope can be reduced by the installation of 60° phase switches into each of 176 signal paths of the antenna. A suitable voltage-controlled UHF phase switch has been designed and tested at 843 MHz. It consists of two varactor diodes in series with a microstrip. Although designed to provide only two phase states, the device works well as a continuous phase shifter with a coefficient of ∼3° per volt. Details of the design, performance and application to the radio telescope are given.

New HI observations of the Magellanic Stream have been made using the Parkes 64 m telescope. These observations highlight in detail its complicated structure and uncover new features of the Stream. The extreme velocity clouds (EVCs) are morphologically linked to the Stream indicating that these HI clouds are very likely truly part of the Stream. Also it is suggested that many of the high velocity clouds seen around the Stream are indeed part of the Magellanic Stream itself, and that the stream consists of many different velocity components in bulk motion.

On 1922 August 20, a 20-strong scientific team, together with a naval party of 10, left Fremantle on one of the major scientific expeditions in Western Australian history. After picking up further personnel at Broome, the party proceeded to the isolated post and telegraph station of Wallal on the northern coast of Western Australia. Their task was to measure with great care the deflection of starlight by the Sun during the total solar eclipse of 1922 September 21. Specially designed photographic equipment of very high quality was used and meteorological conditions were excellent. As a result, measurements were obtained for well over a hundred stars.

Line absorption associated with the 12.2 GHz 20 − 3-1 transition of CH3OH has been mapped towards Sgr A with the Parkes 64-m radio telescope and a 2 arcmin beam. Two concentrations are present, both offset from the continuum peak, with velocities of 18 and 46 km s-1 and line-to-continuum ratios of 0.59 and 0.30. For the higher ratio the column density is almost 1017 cm-2. The concentrations may be associated with a molecular cloud which overlies Sgr A East but lies in part behind Sgr A West.

An acousto-optical spectrograph (AOS) with a high spectral resolution of 28 kHz has been developed for spectral line observations of objects, such as dark clouds, where the line-widths are low. It has been mounted on the 4-m-diameter millimetre-wave telescope at CSIRO Division of Radiophysics at Epping, NSW and successfully tested using 115 GHz Co observations of a sample of southern dark clouds. At 115 GHz the velocity resolution is 0.07 km s-1.

The highest frequency at which a radiotelescope can be used depends on the surface accuracy. The rms error of the surface should be less then l/16th of the shortest wavelength. This should be not only under static conditions but also when the telescope is being driven, under the influence of wind and temperature changes. With this in mind we can trace back the development of the paraboloidal dish since the time when Grote Reber constructed his antenna in Wheaton, Illinois.

The twenty years following the Second World War saw great changes in the research interests of the Observatory at Mount Stromlo, with the early emphasis on solar and geophysical phenomena giving way to stellar and galactic astrophysics. This paper traces the development of the astrophysical research work during the directorships of Woolley, who initiated the change of direction, and of Bok, who continued it. Apart from the shift in the Observatory’s research interests, these years were distinguished by (i) an outstanding period of telescope acquisition, which saw the commissioning of the 74 inch reflector, the 50 inch (formerly the Great Melbourne Telescope), the Yale/Columbia refractor (relocated from South Africa), and the Uppsala Schmidt; (ii) an Australia-wide site-testing programme and the consequent establishment of Siding Spring Observatory with the 40 inch, 24 inch and 16 inch reflectors (the site has subsequently, of course, also become the home of the Anglo-Australian Telescope, the U.K. Schmidt, and the ANU 2.3 m Advanced Technology Telescope); (iii) the incorporation of several major technological developments into the instrument complement of the Observatory, including photo-electric photometry, coudé spectroscopy, spectrum scanners, polarization instruments, and digital computers; (iv) the establishment of the link with the Australian National University and the consequent transformation of the Commonwealth Observatory into the Mount Stromlo Observatory; and (v) the setting up of a large and vigorous graduate school, comprising, at Bok’s departure, about fifteen PhD students on course.