TITLE: GCN CIRCULAR NUMBER: 21957 SUBJECT: GRB 171001A: Nanshan-0.36m optical afterglow detections DATE: 17/10/02 12:21:09 GMT FROM: Dong Xu at NAOC/CAS H.J. Tan (CCU), H.X. Feng, D. Xu, Z.P. Zhu (NAOC), Y.D. Hu (IAA-CSIC), Y. Qin (Geneva Obs.), X. Gao (Urumqi No.1 Senior High School) report: We observed the field of GRB 171001A (Lien et al., GCN 21946) using the 0.36m robotic telescope located at Nanshan, Xinjiang, China. Observations started at 18:37:21 UT on 2017-10-01, i.e, 701 sec after the BAT trigger, and all imaged were taken without filter. The optical afterglow was detected at the XRT position (Evans et al., GCN 21952) with coordinates R.A. (J2000) = 01:28:18.67 Dec. (J2000) = -11:53:39.0 with an uncertainty of ~0.5 arcsec. Our photometry was summarized as follows: ======================================== Tmid(s)+T0 Exptime(s) Mag(R) MagErr 741 40*2 >17.60 902 60*2 17.93 0.13 1102 60*3 18.00 0.11 1328 90*2 18.55 0.11 1522 90*2 18.60 0.20 3327 90*8 >18.75 ======================================== Note: (1) Photometry is calibrated with stars in the USNO B1 catalogue in the R-filter, although images were taken without filter. (2) MagErr is the only statistical error of the measurement. (3) The magnitudes are not corrected for the Galactic extinction.