Left: visual orbit of the Aa–Ab components of β Cen. The MAPPIT observation is plotted as an open circle, speckle data with plus signs, SUSI observations with filled circles. For the last observations, the larger the symbol, the larger the weight that was adopted. The line of apsides is plotted with a dashed line, the line of nodes with a dash-dotted line. The designation of x and y follows the common double-star convention (Heintz 1978). Right: radial velocity curves for both components, filtered to remove any high-frequency contribution (red open circles for primary and blue filled circles for secondary), compared to the solution from combined visual and spectroscopic data (continuous lines). Phase 0.0 corresponds to T₀. The span of the B-C data is also shown.