TITLE: GCN CIRCULAR NUMBER: 11253 SUBJECT: GRB 100906A: GRAS-007 optical observations DATE: 10/09/07 17:19:18 GMT FROM: Veli-Pekka Hentunen at Taurus Hill Obs,A95 Veli-Pekka Hentunen, Markku Nissinen and Tuomo Salmi (Taurus Hill Observatory, Varkaus, Finland) report: GRAS-007 PlaneWave CDK 17" F6.8 telescope and STL-11000M CCD camera (Global-Rent-a-Scope, Nerpio, Spain) were used to detect GRB 100906A optical afterglow. The observations were started at 2010-09-07 02:13:24 (UT) and stopped at 2010-09-07 03:40:53 (UT). A number of unfiltered images with 120 sec and 600 sec exposure time were made. The afterglow was detected at following position RA 01 54 44.12 and DEC +55 37 49.4 consistent those given by Melandri A. et al. (GCN 11229) to within positional errors. The following magnitude was obtained from the observations using USNO-B1.0 1456-0062169 (R = 15.70) as the comparison: +T0 (hour) Filter Exp (sec) Mag Mag err Limit 13:00:24 (midpoint) unfiltered 3x600s 19.8 0.4 21.0 A JPG image of the 3x600 sec observations is available at the following URL: http://cutenews.kassiopeia.net/data/upimages/GRB100906A.jpg