GCN Circular 18155
F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team: UVOT took a finding chart exposure of 28 seconds with the White filter starting 94 seconds after the BAT trigger on GRB 150818A. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 15:21:25.48 = 230.35616 DEC(J2000) = 68:20:34.0 = 68.34278 with a 90%-confidence error radius of about 1.0 arc sec. This position is 10 arcseconds from the center of the XRT error circle (D'Elia et al. GCN Circ. 18152). The estimated magnitude is 19.5 with a 1-sigma error of about 0.2. No correction has been made for extinction.