The U-burst, first identified by Maxwell and Swarup and Haddock, is a type of solar radio event lasting ~ 10 s in which the frequency of the emission at first drifts rapidly downwards, then increases again. On the dynamic spectrum record the burst has the appearance of an inverted letter U.

We have designed and manufactured a multi-purpose electronic, computer-operated blink-comparator and measuring engine. It has been specifically designed to facilitate the examination of stellar images on Uppsala Schmidt photographic plates, identify and establish coordinates of new suspect variable stars appearing on the plates being examined, and also to derive photometric values for those stars manifesting variability.

It can be shown that cepheids pulsating in the first harmonic when evolving through the instability zone at constant bolometric luminosity and mass, are at a given period 0.09 magnitudes bluer than stars pulsating in the fundamental mode. Bell and Rodgers have shown that effective temperatures of cepheids can be obtained by comparison of observed and computed profiles of the wings of the Hα line. Hα cores of cepheids are affected by strongly doppler broadened chromospheric emission and absorption. Using a modified Oke effective temperature-intrinsic colour relation, observations of the Hα line of the Eggen C cepheids β Dor and S Mus have been made at Mt. Stromlo and intrinsic colours obtained for these stars.

The 1.04 m telescope and auxiliary instrumentation conceived some ten years ago, are now operational and starting to produce results. Whilst the original purpose of the telescope was high dispersion spectroscopy alone at Coudé focus, access to a folded Cassegrain focus has been added to enable photometric observations to be made.

Global magnetic structure has been inferred in spiral galaxies from radio and optical observations. The author has developed a three dimensional, quasi-global kinematic dynamo model which demonstrates the possibility of maintaining large-scale magnetic fields by the αω mechanism. Analytical expressions for large-scale galactic magnetic fields near temporal steady states have been derived. Illustrations of the spatial distribution of vector and absolute large-scale magnetic field strength are presented. When coupled with observations this model may help in understanding the maintenance and morphologies inferred for disk and halo global magnetic fields in spiral galaxies.

In the field of cosmic ray galactic studies, two kinds of phenomenon are currently being investigated by members of the Hobart cosmic ray group, led by Dr. A. G. Fenton. In a combined project with the University of South Australia, the University of Tasmania is participating in an experiment whose aim is to locate sources of galactic X-rays in a part of the southern sky inaccessible from the northern hemisphere. The object of the other investigation, which forms part of a joint ANARE-University programme of cosmic ray research, is to elucidate the evidence for intensity maxima from fixed galactic directions in the otherwise isotropic charged primary radiation.

This paper presents a measurement of the diffuse cosmic X-ray background made during the balloon flight described in preceding papers and elsewhere. The data used for this paper were obtained with the actively shielded and collimated detector previously described. The geometric factor of the detector was 1.17 cm2 sterad.

The wavefront from a celestial source is believed to arrive at the outer fringe of the Earth’s atmosphere as a truly plane wave of effectively infinite extent. After propagating through our refractively non-uniform atmosphere this wavefront becomes distorted in shape and exhibits a nonuniform amplitude distribution. At present there is little that can be done to remedy the effects of the atmosphere on wave propagation. However when the wave has been received by the entrance aperture of the observing telescope we should try to design this optical system, including its air-path sections, so as to minimize further distortion of the wavefront. ‘Seeing’ effects within an instrument which concern us in this paper are attributable to air of nonuniform temperature (and hence refractive index) in the sections between the optical components.

A time scale may be defined as a system for dating events. A clock is a device for interpolating between observations of the time scale. From antiquity, time scales have been based on the earth’s rotation; even today, the atomic-based time scale Universal Coordinated Time (UTC) is adjusted annually, or when necessary, to keep it in time with the rotating earth. However, the continual search for greater accuracy in time keeping has led to the adoption of time scales based on other phenomena, so that there are now four classes of time scales in use, as summarised in Table I.

We have secured spectra at high signal/noise ratio in a grid of points across the entire Homunculus Nebula surrounding the peculiar, massive star η Carinae. The data cover the wavelength range 420–1000 nm. Included are parts of the outer nebulosity dating from a prehistoric ejection episode. At a spatial resolution of about 1 arcsec we find dramatic differences in emission Ime ratios and profiles, sometimes in adjacent resolution elements.

In April of this year agreement was reached between the British and the Australian Governments to build a 150-inch telescope for observations of the southern sky.

The agreement specified that:

• (i) the telescope would be built at the Australian National University’s present site at Siding Spring Observatory;

• (ii) the expected cost was $11 million and the telescope would be built and operated on a 50-50 basis as between the two Governments;

• (iii) the telescope would be virtually a copy of the existing Kitt Peak 150-inch design. This was intended to save the time usually needed for the design of a new telescope and, as we shall see, it might lead to considerable savings in cost.

An attempt is made to deduce the form taken by the distribution law for radiative scattering events performed by an atom whose energy—level structure is perturbed under conditions appropriate to the quasi-static limit.

An extensive survey of HI absorption in the spectra of discrete radio sources has been in progress for the past three years at the Parkes radio observatory. One part of the survey comprising sources along the galactic plane north of declination —50° has recently been completed. In this communication we discuss some conclusions concerning the distances of 10 sources drawn from a preliminary analysis of the data.

Observations of non-variable sources of astronomical interest can be ideally undertaken at national radio astronomy observatories whenever possible. By contrast observations of variable sources at sporadic intervals of time, taken at the same observatories, can provide the interest/impetus to observe these sources as often as possible. Since national observatories are overloaded with requests for observations of diverse nature, observations of variable sources cannot be undertaken at these observatories on a daily basis. In consequence dedicated telescopes are required for the continuous monitoring of variable sources.

Ultracompact H II regions are small, dense regions of ionised gas surrounding high-mass stars which are still embedded in their natal molecular clouds. A survey of such regions has been commenced in an attempt to improve our understanding of the processes of high-mass star formation. The initial stages of the survey have involved selection of likely candidates from the IRAS Point Source Catalogue, correlation with radio continuum emission at 4·85 GHz and subsequent observations of methanol maser emission at 6·668 GHz. Preliminary results of the methanol maser survey are given.

The SRC-J and ESO-B Sky Survey copy films are being used to compile a major new catalogue of apparent diameters, axis ratios, and relative bar/ring position angles of inner and outer rings in more than one thousand southern galaxies. This paper presents a preliminary analysis of the data for about two hundred SB rings of both types. It is concluded that the rings have a wide range of intrinsic eccentricities, and more importantly that they have preferred alignments, one mode for inner rings and two for outer rings, with respect to bars.