TITLE: GCN CIRCULAR NUMBER: 7477 SUBJECT: GRB 080319C: Early RAPTOR Observations DATE: 08/03/20 06:07:34 GMT FROM: James Wren at LANL J. Wren, W.T. Vestrand, P.R. Wozniak, H. Davis of Los Alamos National Laboratory report: Our RAPTOR telescopes responded to Swift trigger 306778 (Pagani et al., GCN 7442) at 12:26:30.66 UTC, 33.70 seconds after the trigger. We detect the optical counterpart initially reported by Li (GCN 7441). Our measurements are consistent with those reported by KAIT (GCN 7441 and 7475) and Super-LOTIS (7443). Our images became dominated by the morning twilight at about 12:35 UTC. The unfiltered measurements reported in the following table are calibrated to the USNO-B1 R band. t-mid(s) exp(s) mag mag-err ----------------------------------------- 47.60 5.0 16.97 0.32 85.27 80.3 17.65 0.18 177.36 61.5 18.22 0.36 228.87 61.1 17.32 0.16 293.28 61.7 17.41 0.20 358.12 62.1 17.13 0.16