Comparison of synthetic spectra with the wings of Hα two stars in NGC 6528. Star-06 (T_eff = 4623 K and log g = 1.98 dex) and Star-07 (T_eff = 4776 K and log g = 2.50 dex). The middle synthetic spectrum (in red colour) is the best fit to the Hα wings, and the other two synthetic spectra indicate the shape of the wings when T_eff is changed according to our estimated uncertainty. The marked grey regions were used to evaluate the goodness of the fit. We note the richer and more noisy spectra for these stars as compared to the benchmark stars displayed in Fig. C.1.