TITLE: GCN CIRCULAR NUMBER: 14423 SUBJECT: GRB130420B: GMG optical upper limit DATE: 13/04/20 20:23:53 GMT FROM: Xiao-hong Zhao at Yunnan Obs X.-H. Zhao (YNAO and PSU), J. Mao (RIKEN and YNAO), J.-M. Bai (YNAO) report on behalf of a larger collaboration: We observed the field of GRB 130420B (Page et al., GCN 14421; Oates et al., GCN 14411) with 2.4m Gao-Mei-Gu (GMG) telescope. Observations started at 13:21:14 UT on 2013-04-20 (i.e., 0.4 hrs after the burst). The observations lasted for ~10min. The afterglow was not found at the XRT position, down to a upper limit of R>22.6. We thank the GMG staff, especially Yu-Xin Xin, Gui-Hua He and Jian-Duo He for performing these observations. [GCN OPS NOTE(20apr13): I hav removed their copy-paste double TITLE block.]