Fringe rate as a function of sky position, corresponding to the fringe pattern illustrated in Figure 1. Fringe rates peak at ﹩1.09\;\mathrm{mHz}﹩ at ﹩\delta =0^\circ ﹩, hit zero at the south celestial pole, and become negative on the far side of the pole. Gray shading indicates the approximate angular regions that correspond to alternating fringe-rate bins, assuming a fringe-rate transform taken over a two-hour time series.