Stokes I (left panel) and V (right panel) spectra of the Hα core in HD 24712. Individual intensity spectra (solid lines) shown in the left panel are compared with the spectrum corresponding to phase 0.009 (dashed line). The right panel compares the observed Stokes V signal (thin line) with the weak field model fit (thick line). The spectral detail affecting the intensity profiles at v ≈ 20 km s^-1 is due to a telluric line. Vertical dashed lines on the right panel show the velocity range used for the longitudinal magnetic field measurements.