GCN Circular 20071
A. Melandri, P. D'Avanzo (INAF-OAB), V. D'Elia (INAF/OAR & ASI/ASDC), V. Lorenzi, Hristo Stoev (INAF-TNG) report on behalf of the CIBO collaboration: We observed the field of GRB 161017A (Troja et al., GCN 20064) with the 3.6m Telescopio Nazionale Galileo (TNG) equipped with DOLoRes. Observations were carried out in the r-sdss filter. Observations started on Oct 18 at 03:51:18 UT (~10 hours after the burst) and consist in a single image lasting 120 seconds. 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) is detected with a magnitude r(AB) = 17.9 +/- 0.1 (calibrated against nearby SDSS stars).