GCN Circular 23954
J. Mao, X.-L. Zhang, and J.-M. Bai (YNAO) report: We observed the field of GRB 190311A (Troja et al. GCN Circ. 23946) with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG) station of Yunnan Observatories. The observation began at UT 16:15:07, 11, March, 2019, about 2 hours after the trigger. We clearly detected the afterglow (Pozanenko et al. GCN Circ. 23947; Zhu et al. GCN Circ 23948; Belkin et al. GCN Circ. 23951) , and the preliminary magnitude is measured to be R~20.6.