The appearance of Tech Pan film in sizes that were useful in large Schmidt telescopes immediately offered new opportunities and advantages to users of Schmidt telescopes. Among the advantages were a spatial resolution that was well matched to the image quality produced by the optics of the telescope under the best conditions. For the first time such images were well sampled on Schmidt telescopes. Tech Pan was initially formulated by Eastman Kodak as a 35 mm solar patrol film designed to have enhanced sensitivity around the 656·2 nm Hα line. It is this feature, combined with the excellent imaging characteristics, that we seek to exploit with the new UK Schmidt Telescope (UKST) Hα survey. This paper briefly reports some preliminary comparative tests of Tech Pan with the new Hα filter at UKST and suggests ways in which data from the new survey can be quickly exploited using advanced photographic techniques such as photographic amplification. This simple contact copying process rapidly reveals extended low surface brightness features that simple inspection cannot.

We have performed a uniform and unbiased imaging survey of the Large Magellanic Cloud, using the IRAC and MIPS instruments on board the Spitzer Space Telescope. This Spitzer survey of the Large Magellanic Cloud is surveying the agents of a galaxy's evolution (SAGE), the interstellar medium and stars. The SAGE data are nonproprietary and the team has been creating catalogs and improved images for use by the astronomical community. This paper highlights some of the initial results being published by the SAGE team covering the topics of evolved stars and their mass-loss return to the ISM, young stellar objects and the properties of the ISM dust.

The angular diameter of a star, combined with observed stellar fluxes in absolute units, allows the absolute fluxes emitted at the surface of the star to be calculated and thus provides a stringent test of model atmosphere predictions. Furthermore, if the flux distribution is observed at all wavelengths contributing significantly to the net flux, an empirical effective temperature can be found. Sufficient data are now available for Sirius (αCMa) to be studied in this way.

We evaluate the effect that radome transparency has on atmospheric opacity measurements performed by the skydip technique. We show that, except at rather high opacities, it is not sufficient to ignore losses in the radome (or ‘window’) during the data analysis and then subtract them from the derived atmospheric opacity. Perhaps surprisingly, unless radome transparency is correctly modelled, the atmosphere will appear to have a minimum opacity that is many times greater that the radome losses. Our conclusion is that some previous site studies may have significantly underestimated the quality of the best submilli-metre sites, and that the difference between these sites and poorer sites may be much greater than currently believed. We also show that part of the residual 857-GHz opacity at the best sites, currently ascribed to ‘dry-air opacity’, can in fact be just an artefact caused by not properly modelling the radome during the data analysis.

The recent discovery of two distant satellites of Uranus suggests that there could be similar bodies orbiting Neptune. Previous surveys for distant satellites of Neptune have had relatively bright magnitude limits (BJ ≃ 20·5) and would have missed satellites with magnitudes and colours similar to the two recently discovered Uranian satellites (R ~ 20·4 and R ~ 21·9). We have searched for satellites of Neptune to a limiting magnitude of R ~ 21 in a 0·1□° region centred on the planet. This search is up to ~ 2 magnitudes deeper than the previous wide field search for distant satellites by the UK Schmidt Telescope. Nereid was easily recovered by the search and no large variations of its magnitude were detected.

A test of the hypothesis that flares derive their energy from large scale current systems inferred from active region vector magnetograms is proposed. The test involves a statistical comparison of the flarerelated change in coronal magnetic energy (based on the magnetohydrodynamic virial theorem) and an independent measure of the energy of the flare. A simulation suggests that — assuming the hypothesis is correct—the test requires around 50 flares with energy greater than 5×1023 J to return a significant result. Existing archives of vector magnetograms should provide sufficient data for such a study.

We describe a new polarised imaging pipeline implemented in the fhd software package. The pipeline is based on the optimal mapmaking imaging approach and performs horizon-to-horizon image reconstruction in all polarisation modes. We discuss the formalism behind the pipeline’s polarised analysis, describing equivalent representations of the polarised beam response, or Jones matrix. We show that, for arrays where antennas have uniform polarisation alignments, defining a non-orthogonal instrumental polarisation basis enables accurate and efficient image reconstruction. Finally, we present a new calibration approach that leverages widefield effects to perform fully polarised calibration. This analysis pipeline underlies the analysis of Murchison Widefield Array data in Byrne et al. (2022, MNRAS, 510, 2011).

The effects of charged dust on the steepening of the fields in nonlinear Alfvén waves in astrophysical weakly ionised plasmas are investigated. It is found that the formation of current singularities in the wave due to nonlinear ambipolar diffusion is strongly modified by the effects of the dust. The basic modes for propagation along the magnetic field in a dusty plasma are highly dispersive and split by the anisotropy of the magnetic field into two modes that are oppositely circularly polarised rather than linearly polarised. The right hand circularly polarised wave experiences a cutoff due to the presence of the dust. We derive nonlinear fluid equations describing the dusty plasma, and make approximations for strong coupling of the dust to the neutrals, and for stationary dust. Numerical solution of the equations shows that a nonlinear wave with sharp current features due to ambipolar diffusion involves a rotation of the wave magnetic field about the direction of propagation, and an oscillation of the field components, due to the mode splitting effects of the dust. This is in contrast to the dust-free case, where the sharp reversal of the transverse magnetic field component occurs in a single plane.

While unobscured and radio-quiet active galactic nuclei are regularly being found at redshifts $z > 6$ , their obscured and radio-loud counterparts remain elusive. We build upon our successful pilot study, presenting a new sample of low-frequency-selected candidate high-redshift radio galaxies (HzRGs) over a sky area 20 times larger. We have refined our selection technique, in which we select sources with curved radio spectra between 72–231 MHz from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. In combination with the requirements that our GLEAM-selected HzRG candidates have compact radio morphologies and be undetected in near-infrared $K_{\rm s}$ -band imaging from the Visible and Infrared Survey Telescope for Astronomy Kilo-degree Infrared Galaxy (VIKING) survey, we find 51 new candidate HzRGs over a sky area of approximately $1200\ \mathrm{deg}^2$ . Our sample also includes two sources from the pilot study: the second-most distant radio galaxy currently known, at $z=5.55$ , with another source potentially at $z \sim 8$ . We present our refined selection technique and analyse the properties of the sample. We model the broadband radio spectra between 74 MHz and 9 GHz by supplementing the GLEAM data with both publicly available data and new observations from the Australia Telescope Compact Array at 5.5 and 9 GHz. In addition, deep $K_{\rm s}$ -band imaging from the High-Acuity Widefield K-band Imager (HAWK-I) on the Very Large Telescope and from the Southern Herschel Astrophysical Terahertz Large Area Survey Regions $K_{\rm s}$ -band Survey (SHARKS) is presented for five sources. We discuss the prospects of finding very distant radio galaxies in our sample, potentially within the epoch of reionisation at $z \gtrsim 6.5$ .

Swinburne Astronomy Online (SAO) is an online graduate program in astronomy intended particularly for amateur astronomers, science communicators and educators. SAO emphasises the development of conceptual understanding and good communication skills in astronomy. The use of asynchronous discussion forums is a central feature of SAO. These 'online tutorials' were introduced partly with the intention of breaking down the isolation of distance education, but mainly to provide a venue where students could deepen their conceptual understanding of astronomy and hone their science communication skills while discussing course material with other students and instructors.

In this project aspects of the use of discussion forums in SAO were investigated, with comparisons made between average marks awarded for discussion forum contributions and those awarded for other assessment tasks, plus analysis of the rate at which students post to the forums, and an investigation of whether gender makes a significant difference to participation rate and assessment results. Responses by students to surveys that probe their ability to express themselves and communicate with classmates in this online form of distance education are discussed. Finally, possible implications for the use of discussion forums as a supplement to face-to-face teaching in astronomy are explored.

Creating radio galaxy catalogues from next-generation deep surveys requires automated identification of associated components of extended sources and their corresponding infrared hosts. In this paper, we introduce RadioGalaxyNET, a multimodal dataset, and a suite of novel computer vision algorithms designed to automate the detection and localization of multi-component extended radio galaxies and their corresponding infrared hosts. The dataset comprises 4 155 instances of galaxies in 2 800 images with both radio and infrared channels. Each instance provides information about the extended radio galaxy class, its corresponding bounding box encompassing all components, the pixel-level segmentation mask, and the keypoint position of its corresponding infrared host galaxy. RadioGalaxyNET is the first dataset to include images from the highly sensitive Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope, corresponding infrared images, and instance-level annotations for galaxy detection. We benchmark several object detection algorithms on the dataset and propose a novel multimodal approach to simultaneously detect radio galaxies and the positions of infrared hosts.

We have combined the observational data of the AAO/UKST and Marseille Hα surveys to extract preliminary new results about ionised structures of our Galaxy. This includes the detection of a new large bubble located in the far part of the Carina arm.

We estimated the scale-length of the thin disc with the J and W1 magnitudes of the most probable red clump stars in the Galactic plane, − 0°.5 ⩽ b ⩽ +0°.5, in 19 equal sized fields with consecutive Galactic longitudes which cover the interval 90° ⩽ l ⩽ 270°. Our results are constrained with respect to the solar space density (D* = 5.95), which indicates that the radial variation of the density is lower for higher Galactocentric distances. The scale-length of the thin disc is 2 kpc for the fields in the Galactic anticentre direction or close to this direction, while it decreases continuously in the second and third quadrants reaching to a lower limit of h = 1.6 kpc at the Galactic longitudes l = 90° and l = 270°. The distribution of the scale-length in 19 fields is consistent with the predictions from the Galaxia model and its variation with longitude is probably due to the inhomogeneity structure of the disc caused by the accreted material or other features such as warp and flare.

Theoretical models of high-mass star formation lie between two extreme scenarios. At one extreme, all the mass comes from an initially gravitationally bound core. At the other extreme, the majority of the mass comes from cluster scale gas, which lies far outside the initial core boundary. One way to unambiguously show high-mass stars can assemble their gas through the former route would be to find a high-mass star forming in isolation. Making use of recently available CORNISH and ATLASGAL Galactic plane survey data, we develop sample selection criteria to try and find such an object. From an initial list of approximately 200 sources, we identify the high-mass star-forming region G13.384 + 0.064 as the most promising candidate. The region contains a strong radio continuum source, that is powered by an early B-type star. The bolometric luminosity, derived from infrared measurements, is consistent with this. However, sub-millimetre continuum emission, measured in ATLASGAL, as well as dense gas tracers, such as HCO+(3–2) and N2H+(3–2) indicate that there is less than ~ 100 M⊙ of material surrounding this star. We conclude that this region is indeed a promising candidate for a high-mass star forming in isolation.

We report on the detection of source noise in the time domain at 162 MHz with the Murchison Widefield Array. During the observation, the flux of our target source Virgo A (M87) contributes only $\sim$1% to the total power detected by any single antenna; thus, this source noise detection is made in an intermediate regime, where the source flux detected by the entire array is comparable with the noise from a single antenna. The magnitude of source noise detected is precisely in line with predictions. We consider the implications of source noise in this moderately strong regime on observations with current and future instruments.

In Australia a significant number of women were employed to measure and compute the position of stars for the Astrographic Catalogue at Adelaide, Sydney, Melbourne and Perth Observatories. New archival research has provided evidence that the first women employed in astronomy in Australia were engaged due to this project.

This paper focuses on Mary Emma Greayer, who was employed as a computer at Adelaide Observatory from 1890, and Charlotte Emily Fforde Peel, employed as a star measurer, computer and astrographic assistant at Melbourne Observatory from 1898. The measurement bureaux at Melbourne, Perth and Sydney Observatories are examined within the context of women working on the Astrographic Catalogue in other observatories during the late nineteenth century.

Evidence is presented that individuals, such as Greayer and Peel, were vital to the completion of the Astrographic Catalogue and other astronomical work. Furthermore, it is argued that this evidence points to women having a broader role and greater agency within observatories in Australia and in astronomy than has previously been acknowledged.

Digital signal processing is one of many valuable tools for suppressing unwanted signals or inter-ference. Building hardware processing engines seems to be the way to best implement some classes of interference suppression but is, unfortunately, expensive and time-consuming, especially if several miti-gation techniques need to be compared. Simulations can be useful, but are not a substitute for real data. CSIRO’s Australia Telescope National Facility has recently commenced a ‘software radio telescope’ project designed to fill the gap between dedicated hardware processors and pure simulation. In this approach, real telescope data are recorded coherently, then processed offline. This paper summarises the current contents of a freely available database of base band recorded data that can be used to experiment with signal processing solutions. It includes data from the following systems: single dish, multi-feed receiver; single dish with reference antenna; and an array of six 22 m antennas with and without a reference antenna. Astronomical sources such as OH masers, pulsars and continuum sources subject to interfering signals were recorded. The interfering signals include signals from the US Global Positioning System (GPS) and its Russian equivalent (GLONASS), television, microwave links, a low-Earth-orbit satellite, various other transmitters, and signals leaking from local telescope systems with fast clocks. The data are available on compact disk, allowing use in general purpose computers or as input to laboratory hardware prototypes.

Observational tasks that require photometry of large numbers of objects, or over large fields, are still best approached using photographic photometry. Nevertheless, there are well-known problems in using photographic emulsions as two-dimensional detectors; these include their non-linearity and unknown photometric zero-points. The non-linearity can be calibrated using standard sensitometer techniques but the provision of photometric zero-points (and the verification of the validity of the intensity calibration) can be done properly only by providing a sequence of standards down to the plate limit. One approach to this latter problem, that has recently been revived by Racine (1969), is to use a sub-beam prism as originally suggested by Pickering (1891).

Magnetic fields of about 1012 G have now been measured in several astrophysical objects (Trümper etal. 1978, Wheaton et al. 1979, Mazets et al. 1981). In the case of pulsating X-ray sources, the presence of a companion star indicates that accretion is probably the energy source for the X-rays.

We have deduced the yearly averaged value of the solar diurnal variation as observed by a surface muon telescope and three underground muon telescopes over the years 1957 to 1985. This has allowed us to examine the temporal variation in both the latitudinal gradient Gz and the product of the parallel mean free path and the radial gradient of galactic cosmic rays during three consecutive solar cycles. The median rigidities of the primary particles being detected by the telescopes are 50 GV in the case of the surface muon telescope and greater than 150 GV in the case of the underground muon telescopes. We have compared our results with those of a similar study made from observations of the solar diurnal variation by neutron monitors and an ion chamber, which have median rigidities of response between 17 and 70 GV (Bieber and Chen 1991a). The product has a solar magnetic cycle dependence and our values are lower than those observed by neutron monitors, in agreement with the Bieber and Chen observation that reverses after a solar magnetic field reversal, in accordance with drift theories.