Left: CMD of Trumpler 23 of photometry from Carraro et al. (2006) with all stars within 6′ marked as small grey dots, UVES cluster members as purple circles, UVES non-members as light purple crosses, GIRAFFE cluster members as dark green circles, and GIRAFFE non-members as light green crosses. Star 18, targeted by GIRAFFE, is a cluster member by radial velocity but has inconsistent atmospheric parameters (see Sect. 6) so it is marked with an open green circle. A reddening vector is also marked in the lower left. Top right: the same symbols showing the coordinates of all stars observed in the Gaia-ESO survey and Carraro et al. (2006) stars within 6′. Lower right: the same symbols showing distance from the cluster center vs. radial velocity of all observed stars except for one GIRAFFE non-member at +459 km s^-1. The cluster systemic velocity is marked as a solid line.