Carbon monoxide (12CO) interstellar clouds are widely distributed while clouds of 13CO, HCN, CS and HCO+ are generally more compact. Additionally the molecular lines of the former species tend to be more intense than that of the latter. High resolution and high sensitivity maps of interesting interstellar clouds are, at present, time consuming when a single beam telescope is used. Multiple beam telescopes are therefore required to undertake these mapping tasks during the periods when the precipitable water vapour content of the atmosphere is low; for sites near sea level these periods can be short.

Most extra-galactic radio sources show angular structure over a wide range of size. Long-baseline interferometers and scintillation observations have shown that resolved sources extending over 10′ arc can have significant contributions from components <1″ arc. Observations at low frequency with the Molonglo cross telescope show also that a large fraction of the emission can come from halo, bridge or extended regions which may form a diffuse ridge or arc structure extending well beyond the small diameter components. However the majority of sources exhibit a basic double structure, and this has led to the adoption of two extended (Gaussian) components as an initial model for the interpretation of brightness distribution in most papers on the structure of extra-galactic sources. Parameters based on such a model will usually match the observed distribution quite well, but because of confusion, there is a danger in using intensity parameters for a model component to derive the spectral index for part of the source.

Recent evidence suggests that radial pulsation can explain most of the variability in the majority of well-studied β Cephei stars (Stamford and Watson 1978; Campos and Smith 1980).

An intriguing problem in cosmogony concerns the ability of a planetoid embedded in a nebula disc to clear a gap around its orbit. The application of density wave theory to this problem has demonstrated that a significant exchange of angular momentum can take place between a planetoid and a disc (Goldreich and Tremaine 1980). The torque exerted by the disc on the planetoid can result in orbital drifting of the latter, which may play an important role in the aggregation process (Hourigan and Ward 1983). In fact, in the absence of significant deformation of the nebula, the radial orbital drift rate of a planetoid increases with planetoid mass. In this case, it would be expected that only one or two planetoids would sweep out the nebula, a situation not compatible with present observations. The orbital drift resulting from the generation of density waves therefore requires a limiting mechanism.

Over the past ten years a comprehensive educational program has been developed at Carter Observatory which covers every level from pre-school to PhD. A great deal of time also is expended in a varied adult education program. Every effort has been made to co-ordinate the various parts of the program in such a way that people will be encouraged to take a productive interest in astronomy.

PKS 1318-43 was first identified with the elliptical galaxy NGC 5090 by Ekers (1969) in the Parkes catalogue. Schilizzi and McAdam (1975) mapped the source with 2.9 arcmin resolution at 408 MHz using the Mills Cross, resolving the source into an extended double structure approximately 15 arcmin in extent at p.a. 36°. Schilizzi (1975) also noted a possible optical link with an edge-on spiral (NGC 5091) ~75 arcsec to the south-east. Figure 1 shows a print of the two galaxies taken from the UK Schmidt J survey film. During 1980, in collaboration with K. J. Wellington, RMS mapped the source at 1415 MHz with the Fleurs Synthesis Telescope (FST, Christiansen 1973).

A complete copy of the compressed COSMOS/UKST Southern Sky Object Catalogue is now available on-line at the Anglo-Australian Observatory and the Australia Telescope National Facility. The catalogue lists image parameters for all objects detected to a limit of BJ ≈ 21·5 in the UK Schmidt Southern Sky Survey. We have written software to access the catalogue efficiently and generate finding charts or text listings of the image parameters. In this paper we describe the software and give some examples of its use. We also discuss the astrometric precision of the catalogue.

We present a series of numerical models describing the dynamical evolution of globular clusters with a mass spectrum, based on integration of the Fokker-Planck equation. We include three-body binary heating and a steady galactic tidal field. A wide range of initial mass functions is adopted and the evolution of the mass function is examined. The mass function begins to change appreciably during the post-collapse expansion phase due to the selective evaporation of low mass stars through the tidal boundary. One signature of highly evolved clusters is thus the significant flattening of the mass function. The age (in units of the half-mass relaxation time) increases very rapidly beyond about 100 signifying the final stage of cluster disruption. This appears to be consistent with the sharp cut-off of half-mass relaxation times at near 108 years for the Galactic globular clusters.

There is a difference of opinion as to whether W33, an HII-region/molecular-cloud complex of size about 15′ arc centred near l = 12°.8, b = -0°.2 is a single object or a chance line-of-sight alignment of two complexes at completely different distances.

The discovery of pulsars in 1967 marked the watershed of interest in short-time-scale phenomena in radio astronomy. Ionospheric scintillation on time scales of seconds, interplanetary scintillations at tenths of seconds and solar bursts of similar duration had already been studied. But with pulsars individual pulses contained subpulses of width about 10 ms, and later observations of microstructure were to show that structure with scales of 10—100 μs were present. In other areas searches for the 10—100 ms radio pulses expected to accompany the gravitational wave events resulting from stellar collapses were made, and more recently searches have been made for the radio pulse accompanying the explosion of small black holes (Rees 1977). Work in this area is summarized by O’Sullivan et al. (1978) and Phinney and Taylor (1979).

A small astronomical observatory has been constructed on the edge of the Macquarie University campus at North Ryde in Sydney. It will be used primarily for photoelectric observations of variable stars. Further improvements to the present observing system are being planned and observations have already started on β Cepheids.

Ammonia was searched in the direction of 46 sources placed in the southern hemisphere where H2CO or H2O was detected previously. Observations were carried out at Itapetinga Radio Observatory, Atibaia, Brazil using a 13.7 m paraboloid. The receiver used for these observations had a K-band ruby travelling wave maser as a preamplifier and the system temperature ranged from 250 to 300K. All sources were observed at least twice, each observation lasting for 30 minutes. The filter bank used consisted of 47 contiguous channels with 100 kHz bandwidth. Results are presented on Table 1 — Positive results and Table 2 — Negative results.

This work is aimed at understanding the phenomena which affect the sharpness and stability of optical images transmitted through the atmosphere. A brief description is given of the results obtained to date from an experimental field-study directed at establishing a connection between optics and meteorology. Most of the work has, so far, been conducted in daytime because our main application is to solar astronomy; other fields such as surveying, aerial reconnaissance and so on can also benefit from basic research in atmospheric optics.

A horizontal line of sight over uniform, level terrain presents the simplest case for study. The optical transfer function (OTF) of the system comprising an air-path and telescope objective has been measured with an image analyser which is a modified form of stellar seeing-monitor. The outputs of this analyser are proportional to the modulus and argument of the OTF. The modulus, or modulation transfer function (MTF), is a measure of image contrast; the fluctuations of the argument measure image movement, or “dancing”. The OTF is a function of spatial frequency f (cycles per unit distance) which may be altered by radial movement of the scanning graticule of the image-analvser.

Photoelectric B and V light curves and high dispersion spectroscopic observations were obtained in 1985 February for the rapidly rotating spotted star HD 36705. The visual light range was about 0.09 magnitude, with a well correlated B-V change of approximately 0.04 magnitude, the star being redder when faintest. There is evidence for a broadband flare of ~0.05 magnitude in V and 0.07 magnitude in B. This occurred near maximum light.

Spectroscopic observations show a variation in the equivalent width of the Ca K emission by a factor of about two in antiphase with the photometric variations, maximum emission corresponding to minimum brightness. This is probably due to bright plages and enhanced chromospheric heating associated with the photospheric starspots.

High dispersion, high signal-to-noise spectroscopic observations confirm the presence of lithium λ 6708 as reported by Rucinski (1982, 1985).

Several interpretations of the nature of HD 36705 are discussed; however at present none is completely satisfactory and further observations are required. As the star is probably at less than 100 pc, a parallax determination may be possible, and could help answer many of the questions concerning HD 36705.

Since the discovery of variable circular and linear polarisation in VV Puppis (Tapia 1977), several investigators have observed the system. The new observations particularly of polarisation (Liebert et al. 1978, Liebert and Stockman 1979 have ruled out the standard dwarf nova (accretion disc — hot spot) model previously used to interpret the light curve of VV Puppis.