TITLE: GCN CIRCULAR NUMBER: 15156 SUBJECT: GRB 130831A: THO optical observation DATE: 13/09/01 06:48:23 GMT FROM: Veli-Pekka Hentunen at Taurus Hill Obs,A95 Veli-Pekka Hentunen, Markku Nissinen, Harri Vilokki and Tuomo Salmi (Taurus Hill Observatory, Varkaus, Finland) report: We have detected GRB 130831A optical afterglow at Taurus Hill Observatory A95 (Varkaus, Finland). We used 0.35m C-14 OTA telescope (f =3910 mm), NextGen 0.5X, Paramount ME and SBIG ST-8XME CCD camera. The observation was started 6.65 hours after the Swift trigger. Six unfiltered images with 600 sec exposure time were made. The afterglow was detected at following position RA 23 54 29.7 and DEC +29 25 46.6. The following magnitude was obtained from the observation using NOMAD1 1194-0619856 (R=16.240) as the comparison: Tmid(h)+T0 Filter Exp. time Mag Mag err. 7.218 unfiltered 6x600 18.01CR 0.08 A png preview of the observation showing the position of the afterglow is available at this URL: www.kassiopeia.net/wp-content/uploads/2013/09/GR130831A_comparison.png