Bright star test. Results of the King model fitting on frames of smooth artificial clusters, superposed by three identical stars. The total flux of the cluster is 10⁶ photons. The cases of each star flux of 10⁵ and 4 × 10⁴ photons are shown in panels a) and b), respectively. Panels a), b) display cases when stars are not included in the model fit, and c) when they are automatically identified and fitted (smaller ellipses are for fainter stars originally in panel b)). Tidal radius, r_t, and core radius, r_c, are displayed. Dots mark nodes and indicate initial parameters; for each node series of 100 frames are simulated. Ellipses approximate 1σ scatter of the derived parameters and arrows show their bias. Open circles (panel c)) show M31 clusters from Vansevičius et al. (2009) with V < 20 mag.