Blue line: relation between the observed (ordinates) against the Vsini corrected from Stoeckley’s underestimation (abscissas). This relation was calculated for model He i 4 471 line in stars with pnrc parameters T_eff = 21 000 K and log g = 4.0, inclination angle i = 70°, and η ratios ranging from 0 to 1.0. The red bars indicate Stoeckley’s correction Σ for an arbitrary near critical parameter. The η values indicated in the figure are for the actual (Vsini)_Σ = V(η)sini parameters in abscissas.