ИСТИНА

UBVRI CCD-observations of the optical counterpart of the X-ray nova MAXI J1820+070 with probable black hole, were carried out  from April 2018 to April 2019 on telescopes located in Slovakia and Crimea (18–60 cm). The data covers the stages from the beginning of outburst to quiescence and first rebrightening/ On separate nights, monitoring was conducted to study flickering in different color bands with a time resolution of 15-45 s. The correlation of the optical and X-ray luminosity is found according to our multicolor photometry and the SWIFT data. The changes in the amplitude and shape of a periodic ~0.7-d wave during the decline studied. We have of about 13000 individual frames for 100 nights.