Аннотация:We present the results of MASTER Global Robotic Net optical observations of the region within the LIGO/Virgo S200219ac error-box, triggered during the O3 run. We observed 1124 square degrees inside the 3σ error box during a half month. We present the identified optical transients found during this study, which are not related to gravitational waves, and briefly discuss the MASTER observation strategy.https://iopscience.iop.org/article/10.3847/2515-5172/abc6ad