Center-to-limb variations of the mean intensity of the photosphere at 25 line-levels, normalized to the mean intensity of the continuum at disk center. Upper panel: FeI 630.1 nm line; lower panel: FeI 630.2 nm. The right sides of the figures show the measurements performed in the northern hemisphere as functions of 1 − cosθ (0 at disk center), the left sides show the results for the southern hemisphere as funtions of − (1 − cosθ). From the lower curve to the top one the line-cord index varies from 1 to 25 (line center to continuum level). Parabolic fittings (in red) are superimposed to the observed curves at line cords 1 to 9 and 20. The thin smooth line shows the fifth-order polynomial fitting of the continuum mean intensity, as given by Neckel (2005).