Prior to the advent of the Culgoora 80 MHz radioheliograph position measurements on type II solar bursts were restricted to those made with one-dimensional interferometers. These measurements yielded conflicting evidence on the apparent positions of fundamental and harmonic emission observed at a given frequency; different observers reported the fundamental to be closer to and further from the centre of the Sun than the harmonic. Here we report on two-dimensional observations at 80 MHz made on both fundamental and harmonic emission of a type II event that occurred on 1969 March 2. The observations are shown to be consistent with the hypothesis that the emission is produced as the result of a disturbance moving out from the site of a flare and forming a shock front within an overlying coronal streamer. Both fundamental and harmonic are explained by ‘forward’ emission from the shock front. Observations of the harmonic emission at 158 MHz are also consistent with this model.

We have designed a novel all-reflective optical system for an infrared camera. The camera gives a flat 5 arcminute field with a final focal ratio of f/2.5 when used at the f/15 focus of the Anglo-Australian Telescope (AAT). A 70mm diameter Fabry-Perot filter can be accommodated in a collimated beam, thereby giving narrow-band imaging capability. The design could readily be adapted to other telescopes and focal ratios. Its advantages are no chromatic aberration, no vignetting, no ghost images, low light-loss and excellent image quality.

The barometric coefficient of a cosmic-ray neutron monitor is found to increase with atmospheric depth from ~ 150 mm Hg to 600 mm Hg and then to decrease slowly with depth down to 760 mm Hg (Bachelet et al. 1965; Carmichael and Bercovitch 1969). Bachelet et al. 1965) tentatively attributed this change in the slope of the barometric coefficient versus atmospheric depth curve at 600 mm Hg to the contribution made by muons to the neutron monitor counting rate. Carmichael and Bercovitch (1969) have shown that the contribution to the monitor counting rate made by obliquely incident nucleons may be the real cause. Singh et al. (1970) have derived an expression for the barometric coefficient for vertically incident particles in a neutron monitor which increases continuously with increasing atmospheric depth down to 760 mm Hg, demonstrating more definitely that the above explanation of Carmichael and Bercovitch is correct.

We present UBVRI photometry of the faint and highly erratic cataclysmic variable discovered by Hawkins (1983) from a sequence of U.K. Schmidt plates. Observations using the ANU 2.3 m telescope over two nights in September 1986 show pronounced and repeatable modulation at a binary period of 108.6 min. Dramatic colour differences are evident in the folded UBVRI light curves: in the U band, a single sinusoidal peak is present, while at longer wavelengths, a second red peak dominates at a phase separation of Δϕ = 0.5. This behaviour is strongly suggestive of cyclotron emission from two magnetic accretion funnels in an AM Herculis binary system. Furthermore, the binary period lies in the narrow range of 100-115 minutes that characterizes most of the AM Herculis variables lying on the short side of the 2-3 hour period gap. We conclude therefore that the object is almost certainly a new AM Herculis system, and develop a model in which the blue and red components originate from two non-diametrically opposed cyclotron regions that are characterized by differing electron temperatures and opacities. Predictions are made regarding the linear and circular polarization properties of this important new magnetic variable.

The technique of aperture synthesis is well developed in radio astronomy. When applied to the optical regime, aperture synthesis allows one to partially overcome the blurring effects of the atmosphere and increase the angular resolution of large telescopes to the diffraction limit.

MAPPIT (Masked APerture-Plane Interference Telescope) is a multi-element interferometer which operates at the coude focus of the 3.9 m Anglo-Australian Telescope. This instrument has recently been reconfigured to operate in a dispersed mode so that simultaneous observations in a band of wavelengths are possible. We will discuss this instrument’s new mode and present observations of the double star δ Sco and an angular diameter of the previously unresolved red giant β Gru.

While monitoring Barnard’s star in Ophiuchus for flare activity in August 1969, we accidentally recorded two bright flares on an early type star, 66 Oph. Apart from Andrews’ unconfirmed observation of a flare on a B8 star and Eggen’s report of a flare on the β Cephei Variable, (BO) HD 199 140, no other record of an early type flare star is known to the authors.

In this paper we present maps showing the distribution of HCO+ (J= 1→0 transition at 89.18855 GHz) in the direction of NGC 6334 as a function of radial velocity, lhe observations were carried out in May-June 1979 as part of a larger program of HCO+ observations (Batchelor et al. 1980, 1981) using the Epping 4-m millimetre-wave radio telescope.

Studies stimulated by the interpretation of the Elatina formation in South Australia as a fossil record of solar activity have led to discoveries of previously unnoticed features of the sunspot cycle record and to a theory of origin of the sunspot cycle that postulates a solar core in torsional motion and a magnetomechanical wave that couples to the photosphere. The considerations supporting the solar interpretation of the Elatina formation are gathered together.

The interaction of the solar wind and the Earth’s magnetic field causes the field to be confined within a region shaped like a liquid drop. The solar wind flows past this region, the magnetosphere, without penetrating it. The precise shape of the magnetospheric boundary is of interest for hydromagnetic studies, but these usually begin from assumptions about the nature of the magnetic field. Any specification of the boundary which makes no reference to the field must therefore allow more flexibility in such studies.

The Physics Department at the University of Otago, Dunedin, New Zealand, has over the past three years commenced a research and teaching programme in astronomy and astrophysics. Observing facilities now include two metric wave meridian transit telescopes at a site 6 km from Dunedin and a 16-inch optical telescope, formerly at Mt John, which is now sited 4 km from Dunedin at the Signal Hill observatory built by the University’s Surveying Department for geodetic work.

During the interval May 1968 to March 1969 the 80 MHz radioheliograph at Culgoora has been used in a detailed study of the intensity variations in the pulsars CP 0834, 0950, 1133 and 1919. Some preliminary results for CP 1133 and 1919 have already been reported.

From early experiments in 1966 (Cole 1968) the acousto-optical radio spectrograph has been developed at CSIRO to a sensitive, multi-channel spectral-line back-end. The principles of the instrument are described in detail elsewhere (Lambert 1962; Hecht 1977; Milne and Cole 1977). By means of a Bragg interaction between a laser beam and an ultrasonic beam derived from the radio signal, light is diffracted into an order whose light intensity distribution is accurately related to the power spectrum of the radio signal. In the earlier spectrographs the spectrum was recorded photographically (Cole 1973a, b; Hecht 1973) but this was limited to strong spectral features. To study weak spectral features a stable, linear system was needed with large dynamic range. The combination of an array of photodiodes and computer would be capable of observing these weak spectral features (Cole and Abies 1974). Development since 1974 has been a progressive identification of sources of thermal and mechanical instability and of excess noise in the spectrograph system.

In 1966 McGee, Gardner and Robinson carried out an exploratory search at 1665 MHz for OH in 26 thermal sources in the southern Milky Way and reported emission in 12 sources. Subsequent measurements by Robinson, Goss and Manchester confirmed emission from six of these and detected four additional OH emitters.

Rich clusters of galaxies are a common feature of the large-scale structure of the Universe. Those studied so far, show striking regularities with

1. (a) a smooth radial gradient of number density.

2. (b) ’isothermal’ distributions, which according to Bahcall (1975) have a scatter of only ±15% in the size of their characteristic core radii.

3. (c) their limiting structural diameters are ~50 Mpc (cf. Abell, 1975), if they are identified with superclusters.

4. (d) the magnitude of the velocity dispersion about their centres is generally 600-1000 km s-1, and the velocities are cpnsistent with a gaussian distribution (Yahil and Vidal, 1976; also Faber and Dressier, 1976).

5. (e) The extreme velocities are generally within ±3000 km s-1, and for Coma are ∼2400 km s-1 (Tifft and Gregory, 1976).

6. (f) elliptical galaxies tend to predominate near the centre, spirals in the surrounding loose groups.

Clusters of galaxies appear to contain much more mass than just that of the galaxies which provide most of their optical luminosity. There are two important ways to investigate the structure of their gravitational potential wells, firstly by an analysis of the radial velocities of the cluster galaxies, and secondly by a study of the X-ray emission from the hot gas which forms part of the intra cluster medium. We present new samples of radial velocity data for three clusters, and discuss some simple types of models of the X-ray sources.