TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3297 SUBJECT: GRB 050421: Optical observations at the INT DATE: 05/04/21 07:43:55 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia A. de Ugarte Postigo (IAA-CSIC), J. Furnes, R. Corradi (ING, La Palma), M. Jelinek, J. Gorosabel and A. J. Castro-Tirado (IAA-CSIC Granada), report: "Following the detection by SWIFT/BAT of GRB 050421 (Barbier et al. GCN Circ. 3296), we started observations at the 2.5m Isaac Newton Telescope at Observatorio del Roque de los Muchachos in La Palma. The first 120-s image (in the Sloan i-band filter), started on Apr 21.1858 UT (i.e. 15.7 min after the event). We do not see any object within the reported SWIFT/XRT position. Further analysis of additional i-band images is in progress." This message can be quoted.