A widely reproduced image of the Australia Telescope Compact Array shows five of the six antennas in a compact configuration on the east-west rail track with the moon above them. The image above is a more recent, and shows the ATCA in “hybrid” array configuration with two antennas on the 214m north-south rail spur. The north-south spur was added in 1998 in preparation for millimetre-waveband receivers to be added to the array. As atmospheric absorption becomes greater at shorter wavelengths, a two-dimensional array configuration meant good astronomical images could be made from shorter observations while the celestial source was higher in the sky. (Image credit: CSIRO/Alex Cherney)