TITLE: GCN CIRCULAR NUMBER: 27757 SUBJECT: GRB 200519A: iTelescope optical afterglow detection DATE: 20/05/19 16:37:18 GMT FROM: Albert Kong at NTHU A.K.H. Kong (NTHU, Taiwan) reports We observed the field of GRB 200519A (Sbarufatti et al. GCN 27756) with the T31 0.5m telescope of iTelescope.Net in Siding Spring, Australia. The observation was done with a luminance filter (400-700 nm) beginning at 2020-05-19 15:07:45 UT (about 3.8 hours after the trigger) for 300 sec. The optical afterglow (Sbarufatti et al. GCN 27756) was detected with an estimated magnitude of 19.3+/-0.8 by calibrating with the USNO UCAC5 catalogue.