Most of the galaxy redshifts currently available in the literature have been measured from photographic spectra and are generally based on subjective estimates of the position of the narrow absorption features. In using only the few prominent absorption lines, most of the light from the galaxy is discarded. With the advent of digital linear-response detectors it is possible to obtain accurate and objective redshifts by cross-correlating all or part of the galaxy spectrum with a template galaxy of known redshift (Tonry and Davis 1979, Kelton 1980 and references therein).

The deep interiors of cold, degenerate stars consist of a mixture of elements, either because of primordial inhomogeneities or because of incomplete nuclear burning. However, most existing calculations for the cooling of such bodies (subsequent to any nuclear burning) assume that the only source of luminosity is the heat content of the star. An additional (and potentially much larger) energy source is available if the elements have limited mutual solubility below some temperature. The resulting differentiation and gravitational settling can dramatically decrease the rate of cooling, enhance the number of (potentially) observable low luminosity bodies, and may deplete the atmosphere of heavy elements (if substantial mixing between the atmosphere and deep interior occurs). The observational evidence for these phenomena is equivocal at present.

We present changes in the periods of the double-mode beat cepheid star SX Phe from 1951 to 1987 deduced from observed times of maximum light.

The Buckland Park air shower array is being developed particularly for use as an ultra-high-energy gamma ray astronomy telescope. The properties of this instrument are described with an emphasis on improvements being made to its angular resolution. Some early data are presented to illustrate the way in which the data obtained will be used.

We present an analysis of photometry that we and others have obtained of the suspected two–hour variable K1082 in M15.

The coefficient of atmospheric extinction may change during the night and in fact it often does. This has an adverse effect on the determination of atmospheric extinction by simple Bouguer plot of magnitude against air mass. This effect was studied by Rufener (1964), who introduced for the purpose of accurate photoelectric photometry in the Geneva photometric system the method of two ‘extinction stars’. His method consists of the measurement of two stars of the same colour — one starting at high air mass 2 - 3, the M-star (for French montante = rising) and the second starting simultaneously in the meridian at low air mass, the D—star (for descending).

Most supernova remnants (SNRs) show a ring-shaped radio intensity distribution which is interpreted as the projection of an approximately spherical shell of emission. However, in many cases the ring is neither circular nor complete; in this empirical investigation a major factor responsible for asymmetry is identified and the implications of this discovery are explored.

Mt John Observatory photographic spectra of SN 1987A have been obtained on 111 nights during the first year at resolutions of 1.1 Å (blue) and 1.6 Å (red). The early spectra are dominated by broad P Cygni profiles from neutral or singly ionised species. Ba absorption lines may be present. After six months nebular emission features emerged, including [OI] 630, 636 nm and two unidentified UV lines (367, 375 nm) in the previously dark region below 380 nm. Absorption line radial velocities show steep declines in the first month, but are almost constant or only slowly decline after 100 days. For the Hα absorption minimum the initial decline rate was 690 ± 70 km s−1d−1 and the initial velocity was −20.2±0.5 Mm s−1 (LMC frame). By 1988 Feb the slowest material in absorption was at −2.2 Mm s−1.

The emission maxima of Hα and NaID show anomalous redshifts of about 1.0 Mm s−1. The [OI] lines show no such redshift. Recent [OI] and Hα spectra at higher resolution show ‘fine structure’ in the profiles, indicating inhomogeneity in the ejecta. Hβ, Hγ and Hδ (but not Hα) were all weaker or absent from 1987 late March to early May, but strong thereafter. From about 1987 Mar 18 to Apr 17 Hα showed a bump on the blue side of the emission at 647 nm and a double peak (658 and 668 nm). Absorption bumps in the Hα profile in early spectra (1987 Feb) may be due to circumstellar water vapour.

The Buckland Park air shower array has been used for some time as an ultra-high-energy gamma-ray telescope operating at photon energies of about 1015 eV. Other such telescopes have reported apparent bursts of events from astrophysical objects under study. We report here searches for UHE bursts from 14 southern hemisphere objects studied in our UHE programme. No conclusive evidence has been found for any UHE burst activity from these sources in the period 1986-1988. There is possible evidence for activity associated with 1700-377 and SN1987A.

The optical spectra of the AM Herculis binaries are characterized by extremely complex emission lines whose profiles can be resolved into at least three components which are formed in different regions of the accretion stream leading from the companion star towards the magnetic white dwarf. We present a theoretical model which localizes the formation region of the broad emission line component and provides information regarding the structure of this emitting region. In our model the particle trajectories are integrated in a Roche potential and the volume between the white dwarf and the companion has been divided into two different regimes of motion. In one region the gas escapes from the secondary near the inner Lagrange point and is accelerated along a straight line towards the white dwarf. In the other region the magnetic field is strong enought to divert the gas out of the orbital plane and to channel it towards the white dwarfs surface. The model has been used to interpret radial velocity and velocity dispersion data from the AM Herculis system E1405-451.

We have measured the absorption spectra of the two principal lines of 018H at frequencies 1637 and 1639 MHz approximately in the directions of the sources Sgr A and Sgr B2. The use of 64 x 100 kHz filters enabled us to observe both lines simultaneously. The equipment and methods of observation and reduction are discussed by Gardner, McGee, and Sinclair.

Since its introduction by Högbom (1974), ‘clean’ has been widely used to restore images from the aperture synthesis techniques of radio astronomy. The method iteratively subtracts from the maximum deflection of the image the point source response and so deconvolves it with some loop gain;

where yn = residue image.

xn = deconvolving beam derived by matching the peak of the beam to where yn has the maximum deflection and band-limiting the size of beam within the image,

An = a scalar in accordance with the loop gain applied to the residue image, and

n = iteration.

Ideally, the residue image converges to noise level. In digital processing, the method is implemented with special purpose hardware, general purpose computer, or array processor. In all cases the image to be restored (the ‘dirty’ map), the space-invariant beam used to deconvolve the image (the ‘dirty’ antenna pattern) and the loop gain are stored in binary format in memories and registers with finite wordlength. (Wordlength is an economic factor both in hardware and software implementations).

About 1 km to the east of the township of Windsor, NSW and only 50 ft above mean tide level, stands the remains of one of the first observatories in Australia. Here John Tebbutt established his private observatory and for over 60 years continued a remarkable career as a gentleman astronomer in the best tradition of 19th century Europe.

For more than half a century the theory that the universe is expanding has dominated cosmology. All current cosmological theories, from the various Big Bang models to the various Steady State models, explicitly assume an expanding universe. The evidence in favour of an expanding universe is purely circumstantial, and is based on a “sheer assumption”, (Hubble 1936a) that red-shifts in the light received by an observer on Earth from distant objects are caused by relative motion and hence may be interpreted as Doppler shifts. Hubble (1936b) continues: “…the ever expanding model … seems rather dubious”, and “On the other hand, if the recession factor is dropped, if red-shifts are not primarily velocity-shifts, the picture is simple and plausible. There is no evidence of expansion and no restriction of time-scale, no trace of spatial curvature and no limitations of spatial dimensions.” (Hubble 1936c). These statements are as true today as they were in 1936.

Following a 1989 USA conference on Astrophysics from Antarctica, a number of proposals have been advanced to exploit the great astronomical potential of this region. The most interesting is for an international station at a new site chosen for optimum astronomical performance. Near the highest point of the ice plateau (where the pressure altitude is about 5000 m), the extremely dry cold atmosphere will allow effective observation through many wavelength ranges currently inaccessible from the ground. There is also reason to believe that better seeing than is otherwise obtainable from the Earth’s surface may be achievable. Astronomers interested in future Antarctic observing should co-operate in presenting cases to their governments for support facilities there.