The 6 GHz transitions of the 2π3/2, J = 5/2 excited state of OH are present in emission in the direction of several OH-emission regions (Rickard et al. 1975; Knowles et al. 1976), and in absorption in compact thermal sources (Gardner and Whiteoak 1975). This has suggested that transitions in the next highest state near 13 GHz (J = 7/2) might also be widely observable. A single detection has already been reported in W3OH by Turner et al. (1970). In this paper we report the observation of narrow-band emission in several other sources.

At the centre of the Parkes 64—m radio telescope a region of diameter 17 m has recently been resurfaced to improve its efficiency at high frequencies. The first measurements using this section have been made at 22 GHz, in observations of both continuum sources and water tfapour masers. For these observations the receiver front-end used a mixer cooled in liquid nitrogen, followed by a 5 GHz cryogenic parametric amplifier as a second stage. The option of switching against an offset horn was available and the total system noise temperature was ∽ 750 K.

One of the unusual features of the lenticular galaxy NGC 5128 is the presence of HI absorption (Roberts 1970; Whiteoak and Gardner 1971) and H2CO absorption (Gardner and Whiteoak 1976) against the radio source located near the nucleus. Using the Parkes 64-m radio telescope we have made HI and H2CO observations with improved resolution, and have also detected OH absorption in this galaxy. For the OH and H2CO observations, the equipment and observing procedure have already been described (e.g. Whiteoak and Gardner 1973; Gardner and Whiteoak 1976); for the HI observations they will be described in a forthcoming paper (Whiteoak and Gardner, to be submitted to Aust. J. Phys.).

In November 1975 workers at the Herzberg Institute for Astrophysics in Canada (Avery et al. 1976) discovered cyanodiacetylene in Sgr B2. This molecule is the heaviest yet detected in interstellar space, having a molecular weight of 75 amu, and is the longest linear molecule known.

Observations of the 21 cm line of neutral hydrogen can provide several integral properties of galaxies. The systemic velocity Vsvs indicates the distance Δ via the Hubble relation or through group membership. The integral over velocity of the flux density profile, ∫S dV, immediately yields the amount of neutral hydrogen in the galaxy: MH ∝ Δ2∫S dV (neglecting optical-depth effects). The profile width W and the inclination i (derived from the optical axial ratio), together with the (optical) angular diameter a, supply the ‘indicative mass’ Mi ∝ (W/sin i)2 a △ (Bottinelli et al. 1968; Balkowski 1973), which is a fair estimate of the total mass of the system. In addition, as shown by Tully and Fisher (1976), the profile width is a good indicator of luminosity L. The quantities and L, which are (at least roughly) representative of the amounts of matter and of gaseous and luminous material in the system, give an indication of its composition. Together with the linear diameter a△, these quantities contain clues as to galaxy formation and evolution.

NGC 4945 is a ninth-magnitude southern galaxy orientated almost edge-on to the line-of-sight. De Vaucouleurs and de Vaucouleurs (1964) list its classification as SB(s)cd and its optical dimensions as 17’ x 3’ arc. It is of particular interest because 18 cm OH and 6 cm H2CO absorption has been detected (Whiteoak and Gardner 1973; Gardner and Whiteoak 1974) in molecular clouds in this galaxy which overlie the small-diameter radio source located near the nucleus. In reporting the detection of the OH absorption we suggested that the HI profile in the direction of the nucleus was affected by HI absorption. In this paper we describe a study of the HI distribution which substantiates this conclusion.

The Circinus galaxy (CG) was discovered on a plate of an atlas of the nebulae of the southern Milky Way (Lyngå and and Hansson 1972). The detailed optical properties of this galaxy have been investigated by Freeman, Karlsson, Lyngå and Burrell and will be published in a paper by Freeman et al. (1976). The coordinates of the optical nucleus are (1950).

Owing to the comparative lack of radio recombination line observations of southern HII regions, it has not been so far possible to make an overall interpretation of the data for these sources. However, observations of the H90α and H252α transitions by McGee et al. (1975) and Batty (1974) respectively have usefully extended the frequency range of observations to cover ∼ 0.4 to 8.9 GHz for a few southern HII regions.

The β Cephei variables are a group of short period pulsating variables of early spectral type for which no satisfactory physical driving mechanism has yet been discovered. Further it is not clear what form of pulsation these stars are undergoing. The existence of a beat phenomenon and a phase of spectral line broadening is well established in some of these stars. This extends to observed spectral line doubling in three stars, BW Vul, σ Sco and 12 Lac. Because of the difficulty in explaining these phenomena with purely radial oscillations, Ledoux (1951) first suggested the possibility of non-radial oscillations. Other stars in the group, γ Peg, δ Cet, #x03BE;’ CMa and β Cep have approximately sinusoidal velocity and light curves with little indication of spectral line broadening. For these there is probably no a priori observational need to look beyond purely radial oscillations. It is of course conceivable that different modes of oscillation are present in different members of the β Cephei group. However, if line profiles are calculated for various proposed oscillation modes and compared with the observations, it may be possible to eliminate some suggestions and hence limit the search for an instability mechanism.

Symbiotic stars are at the same time perplexing and rewarding to study. Their spectra contain great numbers of emission lines due to atoms in a range of ionization states from neutral to coronal. The continua are weak and usually unobtrusive: the strongest lines may have equivalent widths of thousands of Angstroms. But the crowding of weak lines complicates their measurement and, often, their identification. Many symbiotic stars probably emit weak lines which currently defy identification, but which cannot be distinguished from their neighbours. It is, however, rather rare to find a strong unidentified emission line.

Surveys of the Galaxy at five frequencies in the range 2 to 20 MHz have been made using the Llanherne low frequency array (Ellis, 1972). The data has been assembled into maps covering the area 320° < £ < 30° and -25° < b < 22° and these are presented in rectangular galactic co-ordinates. Galactic radio spectra in various directions have been obtained, combining the new data with seven earlier galactic continuum surveys. The details of all the surveys used are given in Table I. A new 4.7 MHz map has been plotted from the profiles presented by Ellis and Hamilton (1966).

Pulse arrival time measurements allow the determination of accurate pulsar periods, period derivatives and, provided the data span is at least one year, precise pulsar positions. If observations are frequent and reasonably regular, irregularities in the period can also be investigated. To minimize the effect of possible variations in dispersion measure, it is important that these observations be made at a relatively high frequency, preferably above 1 GHz. To eliminate pulse shape variations due to variable ionospheric Faraday rotation, the pulse total intensity or one of the circular polarizations must be recorded.

Four catalogues based on the survey made with the Molonglo Cross-type radio telescope have so far been completed, the largest of which is MCI (Davies, Little and Mills, 1973). These catalogues were noise limited and had a 5α lower limit of about 0.3 Jy. This paper gives an outline of deep surveys that have been made in order to reach significantly fainter sources, but only in a small solid angle of sky.

I will summarize briefly some results obtained from further studies of the Molonglo catalogues MC2 and MC3, centred approximately at declinations +11° and +16° respectively (Sutton et al. 1974).

It has been known for about 5 years that the flux densities at 408 MHz of some sources change over time scales of a few months, but discovery of these variable sources has been largely accidental during the intensity calibration of various observing programs at Molonglo. This paper describes some results from systematic observation of 254 sources over a 12 month period, through which we hope to better understand the telescope performance, find more identifications in the southern sky, and recognise variable sources. An improved calibration will be applied to digital data from Molonglo observations since 1967 (both surveys and individual source observations), now stored on magnetic tape.