TITLE: GCN CIRCULAR NUMBER: 22197 SUBJECT: GRB 171205A: LCO 1-m telescope observations DATE: 17/12/07 13:36:16 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a large collaboration report: We observed Swift GRB171205A (D'Elia et al. GCN 22177) on December 7, 07:21 UT (2.0 days post burst) with one of the 1-m LCO telescopes in Cerro Tololo in the SDSS ri filters. We clearly detect the optical afterglow (Izzo et al. GCN 22180; Emery et al. GCN 22181; Butler et al. GCN 22182; Mao et al. GCN 22186; Choi et al. GCN 22188; Melandri et al. GCN 22189; Steeghs et al. GCN 22190; Cobb et al. GCN 22192; Volnova et al. GCN 22193) with the following magnitudes: Mid Time     Exposure       Filter       Magnitude (AB) (days)        (s) ------------------------------------------------------- 2.0          5x120          SDSS-R        19.43 +- 0.10 2.0          5x120          SDSS-I        19.19 +- 0.10 ------------------------------------------------------- as calibrated against nearby Pan-STARRS objects.