Up-to-date UBV light and O-C curves analyses of the eclipsing binary V477 Cygni

New and complete UBV light curves and times of minimum are presented for the Algol-type eclipsing binary V477 Cygni (Sp. A3 V+F5 V, mv =8.5, P=2.347 days). The binary orbit of the system is highly eccentric and the system shows an apsidal motion. Using the Wilson-Devinney method, two photometric models, without (MODEL A) and with (MODEL B) third-body light contribution to the total light of the system, are obtained. Period analysis also gives some slender evidence for the unseen third-body in the system with the orbital period of about 157 years. In the MODEL A approximation the apsidal motion period is obtained to be 371 years while it is about 434 years in the MODEL B approximation. The photometric mass ratio ( q~0.75) is in good agreement with the spectroscopic value given by Popper (1968). The masses we obtained are 1.80 +-0.10...and and1.35+-+-0.08R... the radii are 1.60+-0.03and 1.42 +-0.03 for the primary and secondary components, respectively. Absolute dimensions have been compared with the models using a moderate amount of convective overshooting and mass loss given by Claret & Giménez (1991). In the log M - log R diagram both components are located above but close to the ZAMS. It is possible to say from the log T - log L diagram that the secondary component is just coming to the main sequence while the primary is slightly evolved from the ZAMS. The theoretical evolutionary models give an age of 6.4*10^8 yrs for the system.