TITLE: GCN CIRCULAR NUMBER: 9246 SUBJECT: GRB 090424: THO optical observations DATE: 09/04/25 05:35:50 GMT FROM: Veli-Pekka Hentunen at Taurus Hill Obs,A95 Markku Nissinen (Taurus Hill Observatory) and Veli-Pekka Hentunen (Taurus Hill Observatory) report: We used 0.35m C14 XLT telescope with SBIG ST-8XME CCD at Taurus Hill Observatory (Varkaus, Finland) for follow-up observations of GRB090424. The observations were started on April 24, at 19:59 UTC (5.8 hours after the burst) and stopped on April 24, at 23:11 UTC. Sixteen unfiltered 600 seconds images were taken. We detected clear optical afterglow object at the position of RA 12h 38m 05s.12 and DEC +16o 50' 15".2 with respect to POSSII F/USNO-B1.0 which is in good correlation with enhanced Swift XRT-UVOT position. Upper limit for the observations is >20.4 mag. Quoted upper limit has been derived using POSSII F and USNO-B1.0 field stars as reference. Filter Tmid(s) Exp(s) Mag (CR) USNO-B1.0 u 20:14:23 600 19.55+/-0.37 u 20:37:30 600 19.95+/-0.38 u 21:32:48 600 20.15+/-0.34 A jpeg preview of the observation showing the position of the afterglow is available at this URL: http://cutenews.kassiopeia.net/data/upimages/grb090424_ticks.jpg