ИСТИНА

Here we present the results of photometric observations of the black hole candidate Cyg X-1 in primary minimum. These observationswere carried out with the main goal to study in details the variability that was found on the optical light curve of this system,-the small peak on the orbital phase 0.03 (Voloshina & Luyty, 1993). All observations were made with UBV photometer on the 60cm telescope of Sternberg Astronomical Institute in Crimea. For comparison, the particular observations in the secondary minimum were also performed on the orbital phases 0.48-0.53. Our observations are covered 23 nights begining from 1996 up to now. The data for 15 nights only were used for our analysis. The possible explanations of this effect are considered.