VARIABLE-STARS IN THE FIELD OF THE OPEN CLUSTER NGC-7789

Fifteen variable stars have been discovered during four nights of moni toring of NGC 7789. It was possible to determine periods for ten of th ese variables. Seven objects are W UMa-type binaries, in this number f ive are members of the cluster. Among the remaining variables, there a re three further close binaries, one delta Scuti which is a blue strag gler in the cluster, and one multi-modal variable (with indeterminable periods). One of the binaries showed an eclipse-like event; this bina ry is a good candidate for determination of masses of its components a t the turn-off point of the cluster.