TITLE: GCN CIRCULAR NUMBER: 32692 SUBJECT: GRB 221009A: COATLI Detection of the Afterglow DATE: 22/10/11 16:41:09 GMT FROM: Alan M Watson at UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Simone Dichiara (PSU), Rosa L. Becerra (UNAM), Tzveti Dimitrova (ASU), Océlotl López (UNAM), Diego González (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Margarita Pereyra (UNAM), Eleonora Troja (UTV/ASU) and report: We observed the field of the bright GRB 220930A (Dichiara et al., GCN Circ. 32632, Veres et al., GCN Circ. 32636) with the COATLI 50-cm telescope and HUITZI f/8 imager at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir (http://coatli.astroscu.unam.mx) from 2022-10-11 06:05 UTC to 06:39 UTC (40.2 hours after the trigger), obtaining a total of 405 seconds of exposure in each of the g, r, i, and z filters. At the position of the UVOT afterglow (Dichiara et al., GCN Circ. 32632), we detect a source with the following magnitudes and 3-sigma upper limit: g > 20.27 r = 19.48 +/- 0.13 i = 18.49 +/- 0.07 z = 17.92 +/- 0.08 Our photometry is calibrated against the Pan-STARRS1 catalog, is on an approximate AB system, and is not corrected for Galactic extinction in the direction of the GRB. We thank the COATLI/HUITZI technical team and the staff of the Observatorio Astronómico Nacional.