TITLE: GCN CIRCULAR NUMBER: 30628 SUBJECT: GRB 210807A: Tautenburg observations DATE: 21/08/11 11:37:11 GMT FROM: Ana Nicuesa at TLS Tautenburg S. Schmidl, A. Nicuesa Guelbenzu, S. Klose, S. Melnikov, B. Stecklum, U. Laux (all Tautenburg) and J. Greiner (MPE Garching) report: We observed the field of GRB 210807A (Lien et al., GCN 30600) with the Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6kx6k CCD camera. Observations started at 23:19 UT on August 7, about 13 hours after the GRB trigger. For the optical afterglow (Lien et al., GCN 30600; Hu et al., GCN 30602; LaPorte et al. GCN 30618) we measure the following magnitudes: r = 21.66 +/- 0.18, at a midtime of August 7, 23:28 UT, i = 21.25 +/- 0.19, at a midtime of August 8, 01:16 UT, z = 20.52 +/- 0.19, at a midtime of August 8, 01:26 UT. Second-epoch observations were performed the following night. The optical transient was not detected anymore: r 22.2, at a midtime of August 8, 23:34 UT, i 22.4, at a midtime of August 9, 00:38 UT, z 21.2, at a midtime of August 9, 01:20 UT. Given magnitudes are calibrated against the Pan-STARRS catalogue.