Depth of the first null of the K5/M0 III giant 24 Cap: the top panel shows the observed squared visibility for 24 Cap. The depth of the null of the first minimum is 8 × 10^-6, corresponding to a visibility modulus of 0.3%. The non-zero visibility is likely caused by the granulation in the star’s surface. The solid line is the best fit limb darkening disk model, the fit results are shown in the lower panel.