V vs. ΔH_α index of stars located in NGC 6167 region (left panel) and placed in NGC 6193 region and its surrounding (right panel). Symbols are the same as in Fig. 4. Dashed (green) curves are the empirical MS form using Didelon (1982) and Feigelson (1983) parameters. These curves are corrected by the adopted apparent distance moduli for each cluster (see Table 4). Dotted vertical lines indicate the adopted limit to separate H_α emitting objects (see Sect. 3.3).