TITLE: GCN CIRCULAR NUMBER: 10681 SUBJECT: GRB 100424A: D50 optical limits DATE: 10/04/25 09:35:32 GMT FROM: Jan Strobl at AI AS CR,Ondrejov Jan Strobl (1), Martin Jelinek (2), Cyril Polasek (1), Petr Kubanek (2,3), Martin Nekola (1), Matus Kocka (1), Michal Jakubec (1) and Rene Hudec (1) (1. ASU AVCR Ondrejov, 2. IAA Granada, 3. GACE Valencia) We observed the field of Swift GRB 100424A (Hoversten et al., GCNC 10667) with the 0.5m telescope D50 in Ondrejov (Czech Republic), starting at 23:27:02 UT, i.e. 06:54:20 after the trigger. A sequence of 20s unfiltered images was obtained. We coadded 60x20s exposure, obtaining an image with a limitting magnitude Rc~19.3, with an effective exposure time 7.35h after the trigger (23:54UT). We do not detect any new source within the XRT localization (Evans et al., GCN10699). This message can be cited.