OPTICAL VARIABILITY OF SS-433 IN 1978-1996

We present the photometric and spectroscopic observations of SS 433 an d perform their frequency analysis and an O-C analysis of the variabil ity of the orbital, precession, and nutation periods. The irregular va riations in the precession period are confirmed. The orbital period sh ows no variations over an interval of 34 years. The nutation radial-ve locity variations lag behind the nutation light variations by -0.(d)6, which is consistent with the model of a nodding accretion disk. The t ime delay of 0.(d)6 is considered as the time of transfer of tidal per turbations from the outer parts of the accretion disk to its central p arts.