The relative astrometric orbit of the outer component (dashed line) relative to the centre of mass of the inner binary (black plus sign). The black error ellipses (5σ) are our measurements (in some cases too small to be seen), and the black x-signs are the corresponding points on the computed orbit, which in each case fall within the error ellipses. The grey line is the line of nodes, the turquoise plus sign is the ascending node, the magenta plus sign is the periastron, and the arrow shows the direction of the outer orbit.