Example of the method used to determine the temperature and surface gravity for star #151. The locus obtained by varying logg (in cgs units) for each fixed model-grid T_eff in order to fit the hydrogen lines is shown by the solid black line. The loci obtained by varying T_eff at each fixed model-grid logg in order to fit the He I and O I lines, and to fit the metal-line dominated 4950–5600 Å region, are indicated by the red-dashed and the green-dotted lines, respectively. The blue cross marks the intersection of the loci, yielding the adopted atmospheric parameter values.