Since the Molonglo cross-type radio telescope was completed in 1967 July, a considerable proportion of the observing time has been taken with calibrating the pointing of the north-south arm. In a current programme the aim is to obtain accurate positions for sources contained in the flux density catalogue recently prepared by Wyllie. This will provide a uniform set of several hundred positions and flux density calibrators covering the +20° to −90° declination range observable at the Molonglo Observatory.

The over-estimation of the flux density of radio sources near the lower limit of a survey has often been considered in the past. The use of digital recording and analysis techniques now enables a quantitative approach to the problem. Monte Carlo techniques may be used to determine the error distribution, including any systematic bias.

The accurate determination of radio source positions is one of the principal uses of high resolution instruments such as the Molonglo Radio Telescope. A critical stage in this process familiar to all radio astronomers involves the measurement of the instrumental response pattern relative to some accurate time or position marker. Ideally, the analysis procedure should introduce no further errors either random or systematic beyond those which are already present in the data. This is virtually impossible with chart analysis.

The flux densities of 220 radio sources have been accurately measured at 408 MHz in order to provide a useful set of calibration sources accessible to southern radio astronomers. The flux densities are based on a scale defined by absolute measurements. This scale appears to be 10% higher than the commonly accepted CKL scale and about 8% higher than the scale defined by Kellermann when averaged over common sources.

This communication describes techniques, new to radio astronomy, which permit the analysis of electrical signals at radio-frequencies by optical methods.

Two applications will be described: the first is to a spectrograph which gives the instantaneous power spectrum of a single broad-band electrical signal; the second is to the analysis of the signals from a number of aerials of an array in order to form a simultaneous image of the brightness distribution of the region of the sky under observation.

The three objects Tau X−1, Cyg X−l and GX3+1 are the most prominent discrete X-ray objects in the sky at photon energies of ≃ 100 keV.

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.

This paper presents evidence for the existence of a previously unobserved X-ray source in the constellation Cetus. The astronomical significance of an intense X-ray object located so far from the galactic disk has prompted this preliminary report.

The Astronomical Society of Australia was formally constituted at an Inaugural Meeting held at 2 p.m. on Wednesday, 30th November, 1966, in the Grounds of the University of Sydney.

The radio object associated with Sco X—1 noted by Andrew and Purton has been observed at a wavelength of 6 cm with the 210 ft radio telescope at the Australian National Radio Observatory, Parkes. At this wavelength the half-power antenna beamwidth is 4′ arc.

The Universities of Adelaide and Tasmania (UAT) have now collaborated in the preparation of four experiments on British Skylark rockets. Two independent X-ray detectors of total sensitive area 40 cm2 were flown on each of two rocket flights launched in April, 1967. The most significant result of these measurements was the discovery of Cen XR-2 and the measurement of the variation in its intensity and spectrum. The third flight, launched in December 1967, carried three X-ray detectors of total area 140 cm2. One of the main results from this flight, evidence for a new X-ray source at high galactic latitude, will be presented in the following paper.

The study of line-broadening mechanisms puts at our disposal an extremely useful tool for the investigation of physical conditions in plasmas, both stellar and laboratory.

Correlation radiotelescopes have become increasingly important in the last few years in all types of astronomical observations. These instruments operate by multiplying (correlating) the outputs of two separate aerials in order to provide a composite antenna with a range of aerial spacings and orientations. As a general rule this range of spacings is truncated at both the largest and smallest spacings, the largest spacing being determined by the area available or by the cost of the system, and the lowest spacing by either cross coupling between the multiplying elements (as in the Mills Cross type) or by the geometrical size of the elements (as in the compound interferometer type).

Worm-gear drives for astronomical telescopes have associated with them certain requirements which cannot be effectively dealt with by applying standard design methods and parameters, since these drives differ in many ways from conventional power transmission gearing.

The overall aim of the planned astronomical programme at Hobart (University of Tasmania) is to obtain stellar and planetary spectra in the ultra-violet, visible, and infrared regions of the spectrum. The major instruments to be used are a 16-inch telescope, a 40-inch telescope, and a solar spectrograph. Included in the project is a programme of laboratory studies, aimed at making quantitative comparisons of several of the most efficient methods for detecting and recording spectra from astronomical objects with low levels of flux. In addition, several new methods will be investigated. These will be referred to later in this paper.