Comparison between the observed HB of 47 Tuc (triangles) with synthetic CMDs calculated with ΔM_RGB = 0.23 M_⊙ and Y = 0.256, 0.270 and 0.286 (filled large circles), respectively, plus a simulation for ΔM_RGB = 0.28 M_⊙ and Y = 0.256 (dots). Two HB tracks corresponding to Y = 0.256, and masses M = 0.8 and 0.9 M_⊙ (corresponding to ΔM_RGB = 0.12 M_⊙ and 0.02 M_⊙, respectively) are shown as solid lines. All the tracks and synthetic CMDs are shifted by E(B − V) = 0.024 and (m − M)_V = 13.40 (see text for details).