Optical variability of SS 433 in 1978-1996

We present the photometric and spectroscopic observations of SS 433 and perform their frequency analysis and an O-C analysis of the variability of the orbital, precession, and nutation periods. The irregular variations in the precession period are confirmed. The orbital period shows no variations over an interval of 34 years. The nutation radial-velocity variations lag behind the nutation light variations by -0.(d)6, which is consistent with the model of a nodding accretion disk. The time delay of 0.(d)6 is considered as the time of transfer of tidal perturbations from the outer parts of the accretion disk to its central parts.