From 1954 to 1963, CSIRO’s Fleurs field station, located 40 km west of central Sydney, was one of the world’s leading radio astronomy observatories. Fleurs was home to three innovative radio telescopes: the Mills Cross, Shain Cross and the Chris Cross, all of which played important roles in advancing radio astronomy from the 1950s through to the 1980s, when the site was closed. The Mills Cross consisted of 450m-long north-south and east-west arrays of dipoles arranged in a cross configuration. Each arm consisted of two rows of 250 half-wave dipole elements backed by a plane wire-mesh reflector. The Cross operated at a frequency of 85.5 MHz (a wavelength of 3.5m), giving a 49 arcminute beam. The Cross was a transit instrument, which observed a chosen declination strip as it passed through the telescope’s meridian. (Image credit: CSIRO Radio Astronomy Image Archive )