TITLE: GCN CIRCULAR NUMBER: 13878 SUBJECT: GRB 121017A: 1.23m CAHA R-band observations DATE: 12/10/18 00:31:03 GMT FROM: Javier Gorosabel at IAA-CSIC J. Gorosabel (IAA-CSIC, Granada), S. Mottola (DLR, Berlin), report on behalf of a larger collaboration: "We imaged the field of the Swift GRB 121017A (Grupe et al., GCN Circ. 13875) with the 1.23m Calar Alto telescope. The observations were carried out in the R-band on Oct. 17.85440--17.86153 UT (1.11--1.29 hours post burst) with a total exposure time of 2x300s. No optical source brighter than R~20 was found within the XRT error circle."