Jacobi radius calculation method shown for the three OCs from Fig. 2, with each row corresponding to each OC. Within each row, the left panel shows the cluster mass as a function of radius from the centre of the cluster, where the blue line is our calculated total cluster mass with a shaded uncertainty region, and the orange line is the theoretical Jacobi mass for a cluster of that size given Eq. (2). The intersection of these lines is the cluster’s r_J. The right panel in each row shows the cluster in an arbitrary coordinate frame centred on the cluster centre. Member stars within r_J are shown in orange, with member stars outside of r_J shown in blue. r_J is indicated by the dashed red line. The dotted purple line denotes our approximate calculated King (1962) tidal radius for each cluster from Paper II. (Adapted from Hunt 2023.)