THE OPTICAL-TIME DELAY IN THE DOUBLE QUASAR Q-0957-A, Q-0957+561-B(561)

We propose a method for estimation of the time delay between identical time samples with unequidistant data. We carried out an analysis of t wo published optical data sets (Vanderriest et al. 1989; Schild 1990) of Q 0957+561 A, B, the first gravitational lens. It is determined tha t the time delay between the arrival of wave fronts from the images A and B is 1.45+0.04 yr. Using Monte-Carlo simulations, we compare relia bility of time delay determination methods and define the confidence p robability of our result better than 99%. The problem of microlensing effects is briefly discussed.