A typical stellar spectrogram shows a vast number of spectral lines. Each of these has its characteristic shape and strength which must, in some way, reflect the structure of the atmosphere in which the radiation arose. It seems reasonable that from all this profile data we should be able (and with considerable redundancy) to infer a good deal about the physical structure of the radiating gas, and a major effort has correspondingly been devoted to clarifying the physical basis of spectral line formation, i.e., exactly how the atmospheric structure and the atomic properties are reflected in the line profiles. This problem, however, is far from solved : Few, if any, of the profiles of strong lines can be predicted in detail from model atmospheres, nor have analyses of the profiles yielded unambiguous data on the atmospheric structure. Indeed, as recently as 1967, the participants at a conference in Bilderberg (Holland) concluded that no data at all which had been obtained from line profile analyses was worthy of inclusion in specifying the solar atmospheric model. Evidently, then, the problem of line formation is not trivial ; in this paper we discuss some of the difficulties and review the not inconsiderable progress which has been made in this area of astrophysical research.

A sample of 339 extragalactic radio sources, noted as extended or multiple in the Molonglo Reference Catalogue, has been observed with the Molonglo Observatory Synthesis Telescope at 843 MHz. It is found that the strong sources all have edge-brightened morphology, while weak sources may be edge-brightened or edge-darkened. The morphological classification of Fanaroff and Riley is not a sharp division by luminosity. The degree of edge-darkening or edge-brightening is better parametrised by one-dimensional moments along the major axis than by the ratio of the separation between brightness maxima to the total extent as used by FR.

I shall outline the physical principles on which I believe pulsar magnetosphere models should be based. The principles follow from the equations of continuity and motion for each species and the two sourceless members of Maxwell’s set of equations, together with the steady-rotation constraint and boundary conditions at the stellar surface.

The Fault Diagnosis Expert System for the Australia Telescope analyses ~12000 items of monitor data every minute that report the health and stability of specific components and signal pathways in the array. These data are divided into signatures which are matched against signatures of known failure modes to diagnose problems with the array. Knowledge about many of the failures is acquired by generating them in earlier tests. The system keeps a six-hour history of the detailed behaviour of all monitor data as well as the visibilities. It archives the data in half-hour intervals, characterising the interval with a small set of robust statistical estimators. An interactive graphical user interface allows the simultaneous display of twenty-four histories of either the 6-hour data or one week of the characterised data, together with options for plotting one history against another and for calculating their robust regression.

The present knowledge of atomic spectra is quite impressive but is far from satisfying all needs in fields such as astronomy. The first and second spectra of many elements have been analysed into energy levels but the spectra of the rare earths and many highly ionized atoms are largely unexplored. However the spectra of Fe I, II and III are now fairly well analysed.

The Teff (effective temperature) scale for M dwarfs is very uncertain. One method which can be used to establish this scale is to compare observed spectra to synthetic ones derived from appropriate model atmospheres. With this method the adequacy of the model atmosphere is of great importance and simple models can give incorrect results. Alternatively if the Teff scale is known with some accuracy then this comparison is a good test of the adequacy of the models. We have computed some new and preliminary model atmospheres for late type dwarfs which accurately treat the line opacity with the opacity sampling technique and employ laboratory values for the transition strengths of molecular bands. With the above two considerations in mind we compare the fluxes of these models to observed fluxes of late K and early M dwarfs. This preliminary analysis indicates a discrepancy with the currently accepted Teff scale for early M dwarfs with the models suggesting values some 200 K hotter.

The Corona Australis cometary globule is a large southern object known to be a region of slow star formation. We have mapped the complex in the 21cm hydrogen line and preliminary results are reported in Llewellyn et al. (1981) and Taylor et al. (1981). The most extensive A, map of the region is given by Rossano (1978) and is based on star counts.

At previous meetings of the A.S.A., brief reports have been made of a new theory for the formation of the solar system which is being developed at Monash University (Prentice 1972, 1977, 1978a, b; Hourigan 1977). This work is nearing completion and on this occasion an outline of the whole theory is presented.

From 1951 to December 1964 the Radiophysics Division of CSIRO regularly operated a solar radiospectrograph at Dapto, N.S.W. This instrument finally spanned the frequency range from 5-2000 MHz with 8 separate receivers, 6 of which used mechanical tuning. Simple rhombic aerials were used on all bands except the 200-2000 MHz band which used a parabolic reflector. The quiet sun could be detected on the latter band only.

During 1965 a section of this spectrograph covering the frequency bands from 10-210 MHz was moved to the CSIRO Solar Observatory, Culgoora, N.S.W., and operated as an interim measure to maintain continuity of observations during the installation of the 80 MHz radioheliograph.

In this contribution, which is an expanded version of an invited lecture at the 1982 A.G.M. at Noosa Heads, the author recalls some of the early work in radio astronomy from Dover Heights.

Crannell et al. (1978) have reported an observed correlation between the time profiles and flux densities of impulsive hard X-ray and microwave solar bursts. We report here on a significant correlation between the flux density of extended bursts of hard X-rays and micowaves. These extended events follow after impulsive bursts and last much longer (see e.g. Fig. 1, Frost and Dennis 1971). However, as extended bursts only occur during very large flares the number of cases available for study is small. The significance of our observations follows from the suggestion of Wild et al. (1963) that the extended bursts are evidence for a second-phase acceleration process in the corona. We show that the observed characteristics of these extended microwave bursts (viz. a rather flat spectrum below a turnover frequency which is independent of intensity) can be explained by gyro-synchrotron radiation from the same population of energetic (E ≈ 100 keV) electrons as those emitting (thin-target) X-ray bremsstrahlung. A detailed source model is discussed in a companion paper (Nelson and Stewart 1979 — Paper B).

The star-formation process is an outstanding and largely unsolved problem in astrophysics. The role of magnetic fields is unclear but is widely considered to be important at all stages of protostellar evolution, from cloud collapse to ZAMS. For example, in some hydromagnetic models, the field may assist in removing angular momentum, thereby driving accretion and perhaps bipolar outflows.

Spectropolarimetry between 8 and 13μm provides information on the direction of the transverse component of a magnetic field through the alignment of dust grains. We present results of 8–13μm spectropolarimetric observations of a number of bipolar molecular outflow sources, and compare the field directions observed with the axes of the outflows and putative disk-like structures observed to be associated with some of the objects. There is a strong correlation, though so far with limited statistics, between the magnetic field and disk orientations. We compare our results with magnetic field configurations predicted by current models for hydromagnetically driven winds from the disks around Young Stellar Objects (YSOs). Our results appear to argue against the Pudritz and Norman model and instead seem to support the Uchida and Shibata model.

Several methods are available for sensitizing photographic plates, each with its own disadvantage. Pre-flashing greatly increases the plate background and is useful only for enhancing the plate’s response to light levels near the plate’s threshold. Baking and (or) evacuating enhance the plate’s response at all light levels and leave a slightly higher background. Unfortunately all of these methods produce plates with a short shelf life after sensitization.

The authors discuss the light-pollution prevention ordinance passed by the Japanese town of Bisei in 1989.

There are many thousands of photographic star plates in observatories throughout the world, and the number is being added to continually. A major difficulty in making use of the information contained in them lies in the measurement of position, and other data, of star images on the plates, and in bringing the data to a form suitable for computer processing. Manual methods are impossibly slow and laborious for an extended program of measurements, and automatic machines on the market are prohibitively expensive for small observatories with limited resources.