Photometric variability of SS 433 (V1343 Aql) in 1979-1981.

V-band photometry of SS 433 during 1981 is reported; the 164 d and 13 d variability cycles are confirmed. All available photometric observations of SS 433 during 1979-1981 are assembled, and the characteristic features of the light variation are analyzed. This 3-yr series of data yields a precession period of 164 + or - 1 d and an orbital period of 13.086 + or - 0.006 d. SS 433 reaches peak brightness at times when its 'relativistic' emission lines achieve maximum separation; the orbital light curve then most closely resembles that of Beta Lyr eclipsing variables. The 13 d orbital variability has smallest amplitude near the 'crossover' dates when the relativistic emission lines coincide. The new observations corroborate the model of SS 433 as a massive eclipsing binary with a bright, 'slaved' accretion disk.