GCN Circular 20072
C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica) on behalf of a large collaboration report: The 1-m LCOGT McDonald telescope began observing Swift GRB161017A (Troja et al., GCN 20064) in the SDSS r filter on October 18, 10:03 UT (~0.67 days since the GRB). We detect the optical afterglow (Yurkov et al. GCN 20063; Troja et al. GCN 20064; de Ugarte-Postigo et al. GCN 20069; Fujiwara et al GCN 20070; Melandri et al. GCN 20071) with r=18.95 +- 0.10 mag at 0.68 days mid epoch, as calibrated against nearby SDSS stars.