Proper motion vectors relative to the mean proper motion of NGC 2244, on top of a DSS red image shown in grey scale. Stellar positions marked by black points are the point of origin for the bars showing proper motions. The orientations of the bars and their colours indicate their direction of motion. The colour segregation in the central part of the image indicated that many stars in the cluster NGC 2244 move away from its centre. The white star indicates the position with the highest surface density of stars, which we adopt as the centre of NGC 2244. For a zoom into some particular regions of this plot, see Figs. D.1 and D.2.