Combined common proper motion plots for those companions for which we have two astrometric measurements. In each case the epoch 1 positions are aligned to [0, 0] and plotted with a black circle, and the change in relative astrometry (i.e., the vector motion) between the epochs is indicated in red for background objects and blue for companions. The black line and black cross indicate the expected motion of a background star, and the expected position of background stars at the second epoch, with the dominant error being the accuracy of our astrometry. Note that this position is the same for all background objects, since it is derived from the proper motion and parallax of the foreground object. The HD 158815 points are partially transparent for clarity. Some systematic errors are seen, which are discussed in the text.