Wesselink radii of 33 classical cepheids

The radii of 33 classical cepheids are determined. We have used the simultaneous radial velocity and photoelectric observation of 15 cepheids of Gieren (1981, 1982a). We have suggested that the best phase alignment between the light and the radial velocity curves in different epochs of 18 cepheids appears when the points of the phases at equal radius on the V, (B-V) diagram are transformed from a loop into a straight line. In such way we have determined the radii of 18 cepheids.