Our programme stars in the colour magnitude diagram, selected from Yadav et al. (2008), all with a high probability of membership. The red symbols correspond to our targets: solar twin Y1194 (red circle), turn-off stars (red rectangles), subgiant stars (red triangles). The blue, magenta, and red solid lines correspond to the isochrones for an age of 4 Gyr, = 9.70, and initial metallicities of [Fe/H] = 0.0, 0.05, and 0.1 from MIST (Dotter 2016; Choi et al. 2016), respectively.