Search for internal rotation of the clusters M3 (top), M13 (centre), and M92 (bottom). For each cluster, 4 radial annuli around the cluster centre are shown, with radius increasing from left to right. The stars in each bin were divided into two subsamples under the assumption of different rotation axes and the difference in mean velocity was calculated. The position angle is zero when aligned in east-west direction, and increases anticlockwise. The extent of the radial bins is indicated in each panel.