Panel a) red solid boxes show the mean positional error of the centroid for true clusters in sky test field 1 and the standard deviation (vertical error bar) vs. N_p. The clusters are binned in N_p, with the bin width indicated by the horizontal error bar. The black solid circles represent the corresponding trend for the distance between the cluster centroid and the simulated source position.Panel b) the distribution of the distance between the simulated source position and the cluster centroid, expressed in arcsec, for ε = 0.10 deg (black line), ε = 0.15 deg (blue line), and ε = 0.20 deg (red lines). Panel c) the cumulative distributions corresponding to panel b).