Yesterday’s ADAP describes the variable baseline interferometer, used at the Parkes Observatory in the late 1960s and early 1970s, which combined the signals from the 18m (60-foot) “Kennedy” antenna (Giyalung Guluman) and the 64m (210-foot) Dish (Murriyang). This innovative system allowed the one-dimensional structure of radio sources to be determined in about 15 minutes, as opposed to the months required by fixed-spacing interferomemters elsewhere. The image above is a variable baseline visibility record of the double-lobed radio galaxy Pictor A showing the fringes and the classic double-source amplitude modulation. The x-axis is the baseline length in feet, with the amplitudes at two frequencies (467 and 1401MHz), measured simultaneously, plotted. (Ron gives more details of the variable baseline interferometer in a video available from the Parkes 60th webpage .)