Spectroscopic targets (red squares) observed in NGC 6553. Left panel: (K, J-K) CMD of the cluster (gray dots) with highlighted the target stars for which we measured chemical abundances (from Valenti et al. 2007). Right panel: position of the targets in the plane of the sky with respect to the cluster center (cross). The dashed black circles have radii equal to one, two, and three times the core radius, which is r_c = 0.53′ (Harris 1996).