Distributions of the member stars (dots) of clusters in the 2D spherical Galactic coordinate system for four open clusters (UBC 46, NGC 869, NGC 884, and UBC 192). The red and blue fitted ellipses are assigned as in 50% and 5% of the peak stellar number density of each cluster, with the red and blue asterisks being their centers, respectively. The solid green line in each cluster is the distance between the centers of inner and outer fitted ellipses regarded to the dislocation of cluster morphology (Hu et al. 2021a,b), namely, the stability of the shape of clusters. The corresponding blue dashed lines are coincident with the directions of the semi-major axes of the outer ellipses, which indicate the elongated directions of clusters.