HR diagram showing the parameter space available from the MILES library. Dartmouth isochrones (Dotter et al. 2008) are overplotted for metallicities close to those of the six analysed globular clusters: [Fe/H] = −0.1, −0.8, −1.3, −2.2 dex, with [α/Fe] = 0.2, 0.4, 0.4, 0.4 dex, respectively, and ages = 13 Gyr for all cases. The colours of the dots indicate the metallicity range closer to the isochrones. The dashed black lines are the adopted limit for selecting RGB stars from MILES used as reference for the fits.