The globular clusters 47 Tuc (NGC 104) and NGC 6723 both belong to the group of clusters which have late-type integrated spectra and which appear to be only slightly metal deficient with respect to the stars in the Hyades.

Primary cosmic rays passing through the solar system carry with them valuable information about solar and astrophysical phenomena in the form of intensity and spectral variations. In order that this information be efficiently extracted from observations of the directional cosmic-ray flux at the surface of the Earth, it is essential to have accurate information available to enable the relating of the observed secondary cosmic-ray directions of motion and intensity to those outside the range of the disturbing terrestrial influences.

The occultation of a star by a planet of similar brightness allows accurate determination of the planet’s radius R, mean density ρ and of the ratio T/μ, where T and μ are the planetary atmospheric temperature and mean molecular weight. These quantities are important for the formation theory of the planet and of its atmosphere (see e.g. Öpik).

Two-colour photoelectric light curves have been obtained for 9 SMC and 7 LMC variables, with periods in the range 1.24-6.61 days. Because of crowding problems, satisfactory observations could be obtained only for cepheids in the outer parts of the Clouds. The LMC cepheids are in the vicinity of NGC 1805-1818, in a field studied at Herstmonceux. The majority of those in the SMC are immediately south of NGC 362.

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.

Wildey (1961) and Tifft (1963) have both done photographic photometry in two colours of 47 Tuc. They found a colour-magnitude (c-m) relation which is characterized by a very short red horizontal branch and a giant branch which is redder at a given magnitude and fainter at a given colour than that of any other globular cluster. Eggen (1961) obtained an ultraviolet excess of 0m.19 for 8 cluster members bluer than B-V = 1m.4 and of 0m.21 for 7 stars redder than this, assuming negligible reddening for the cluster.

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.

This note describes a method of image formation which i applicable to radio astronomy. AH the information simultaneously reaching an aerial array from an extended region is utilized to produce the image so that the maximum sensitivity is realized. The method is simple in principle and involves relatively few components. One stage of the data processing presents some technical difficulty, but it is believed that particularly for observations below about.

The Narrabri Stellar Interferometer has been used to observe the binary stars α Virginis (April 1966) and γ2 Velorum (January 1968).

Theoretical Hα profiles have been used by Rodgers and Bell (hereafter denoted by RB) to obtain the effective temperatures of several cepheid variable stars. They find that the profiles are sufficiently sensitive to temperature to enable them to determine temperatures which are accurate to within about 300°, while being insensitive to other factors such as gravity or the form of the temperature distribution in the model atmosphere.

A preliminary investigation of this cluster was carried out by Gascoigne and Ogston (1963). They found that the cluster is probably a disc type globular on the basis of the c-m diagram down to the horizontal branch and its integrated spectral type (G2).

From an assessment of recent high-resolution galactic radio surveys, in the continuum and in the H109oc recombination line, the author has detected or confirmed over 90 non-thermal sources, most likely all supernova remnants.1 The distances to each of these objects have also been estimated, from an empirical surface-brightness linear-size relationship derived from 15 remnants whose distances are known from either a comparison of the radial velocities and proper motions of filaments in the nebula, neutral hydrogen absorption measurements, or association of the remnant with an object of known distance. In this note we wish to remark on the galactic distribution of supernova remnants and the possible association of these objects with pulsars and X-ray sources.

The Sydney University one mile cross-type radio telescope at the Molonglo Radio Observatory has been used to study the 30 Doradus nebula with high resolution (~3´ arc) at 408 MHz. This preliminary report compares these observations with Balmer line isophotes published by Faulkner. A description of the calibration procedures used in the present observations, an analysis of the various radio features in the 30 Doradus region, and a comparison with previous observations at other frequencies, will be described in a later paper.

The present knowledge of atomic spectra is quite impressive but is far from satisfying all needs in fields such as astronomy. The first and second spectra of many elements have been analysed into energy levels but the spectra of the rare earths and many highly ionized atoms are largely unexplored. However the spectra of Fe I, II and III are now fairly well analysed.

In solar physics a need exists for filters which have very narrow passbands, ~0.01 nm or less. While Lyot-Öhman birefringent filters have been used particularly for investigations at the Hα line, the limited availability of the raw materials, especially calcite, have usually restricted these filters to passbands of ~ 0.025 nm or more. A possible alternative type of filter consists of a number of Fabry-Perot interferometers mounted one behind the other.

The naked-eye cluster, Messier 7, is situated in the constellation of Scorpius, south of the great Sagittarius star clouds, and close to the galactic centre.

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.