The figure shows the reachability-plot resulting from the clustering analysis of the data set comprising the 190 stars of the optimizing sample, 112 stars of the hidden cluster sample, and the 465 stars of the field stars sample. The open cluster members of the optimizing sample are shown with coloured points. All the other stars are represented as gray points. The solution represented here corresponds to the one that maximises the number of recovered clusters from the optimizing sample (N_cl). The overdensities found by OPTICS corresponding to the recovered open clusters are highlighted with vertical coloured bands.