TITLE: GCN CIRCULAR NUMBER: 23485 SUBJECT: GRB 181201A: optical observations in Chilescope observatory DATE: 18/12/02 13:19:51 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), A. Pozanenko (IKI), E. Mazaeva (IKI), A. Volnova (IKI), M. Krugov (AFIF) report on behalf of IKI-FuN follow-up collaboration: We observed the field of the INTEGRAL GRB 181201A (Mereghetti et al., GCN 23469) with RC-1000 telescope of CHILESCOPE observatory. Observations started on Dec. 02 (UT) 01:11:25 in r'-filter. We detected optical afterglow (e.g. Podesta et al., GCN 23470; Kong, GCN 23475; Lipunov et al., GCN 23476: Volnova et al., GCN 23477; Heintz et al., GCN 23478; Mazaeva et al., GCN 23479). Preliminary photometry is following. Date UT start t-T0 Filter Exp. OT Err. (mid, days) (s) 2018-12-02 01:11:25 0.9416 r' 300 18.00 0.05 The photometry is based on the SDSS DR12 star SDSS-DR12_id r J211710.81-123706.3 16.517