Introduction

Flux density calibration of ATCA observations has to date relied almost exclusively on the source 1934-638, using absolute flux densities determined more than 20 years ago. Most ATCA observations use, either directly or indirectly, a polynomial fit of $\log\,$Flux versus $\log\,$Frequency originally derived by G. White (16/10/89), who used the flux densities from the Parkes Catalogue and the MRC flux at 408MHz. This polynomial is currently implemented in the on-line calibration software at the ATCA, and in the AIPS and MIRIAD reduction packages.

It is now clear (Reynolds, E-mail Bulletin, Oct 93) that either 1934-638 has varied substantially since the epoch of the Parkes Catalogue, or that the Parkes Catalogue flux scale differs significantly from more recent determinations, principally that of Baars et al. (1977). This document compiles the best recent flux measurements of 1934-638, placed on a scale consistent with those in use at Northern observatories, from which an improved polynomial fit is derived.