Projected separation of β Pictoris c as a function of time. Top row: data (black error bars) and models (same coloring as Fig. 1). Bottom row: same data but after subtraction of the median orbit of the two-planet model fit from b and c astrometry. The two-planet model that uses only b astrometry (in teal) only weakly constraints the angular separation of planet c, and a direct detection of planet c is needed to obtain precise orbital constraints.