The fringe pattern at 150 MHz of a fiducial 30 m east–west baseline, overlaid with arrows indicating the distance traversed by sources at various declinations over a two-hour time span centered at transit. In a fixed time interval, sources near declination ﹩\delta =0^\circ ﹩ traverse more fringe periods than sources nearer to the celestial poles. This gives rise to different fringe rates that can be used to distinguish sources in a time-series measured with a single baseline.