Condensed tree graph for HDBSCAN with m_clSize = 80 applied to a 2.5° field around Blanco 1, a nearby cluster without any other known OCs in the field. The colour and width of each icicle denotes the number of stars remaining in the cluster. Horizontal splits occur when clusters are no longer connected. The long icicle on the left is Blanco 1, which is an extremely clear, nearby cluster and hence splits early from field stars. On the right, the algorithm continues discarding field stars, splitting into two very short icicles at the end which are false positive clusters. The two small sub-plots in the lower right are zoomed in on the two small icicles.