Spectroscopic Hertzsprung-Russell diagram showing the ZAMS line for different adopted values of the mixing length parameter α_MLT for single-star evolutionary models at Z = 0.0092 with v_i = 150 km s⁻¹. On the left are the ZAMS lines for α_MLT = 0.5 (teal), α_MLT = 1.5 (orange, the standard value), and α_MLT = 5.0 (pink). They overlap for all but the highest considered masses. The middle lines mark the midpoint of the MS, determined as the point where half of the initial hydrogen has been burned in the core. These midpoint lines are for the same 3 α_MLT values as for the ZAMS lines. The lines on the right mark the TAMS lines, for the same 3 α_MLT values. The α_MLT = 0.5 line (teal) terminates at 43 M_⊙ and the α_MLT = 1.5 line (orange) terminates at 72 M_⊙, due to the models failing to converge above this point.