TITLE: GCN CIRCULAR NUMBER: 22230 SUBJECT: GRB 171209A: Lulin 1m telescope observations DATE: 17/12/10 17:59:29 GMT FROM: Albert Kong at NTHU GRB 171209A: Lulin 1m telescope observations A.K.H. Kong (NTHU, Taiwan) reports We observed the field of GRB 171209A (LaPorte et al. GCN 22213) with the 1m telescope at the Lulin Observatory in Taiwan. The observations were done with the SDSS r and i filters and the first observation were started at 2017-12-09 20:20:16 UT (5.6 hours post burst). We detect the optical afterglow identified by the UVOT and LCO (Guidorzi et al. GCN 22214). We obtained the following magnitudes: Start time Exposure Filter Magnitude (AB) 20:20:16 300s SDSS-r 19.47+/-0.11 20:25:50 300s SDSS-i 18.97+/-0.09 The magnitudes were calibrated with nearby Pan-STARRS objects.