TITLE: GCN CIRCULAR NUMBER: 21140 SUBJECT: GRB 170524A: D50 optical observation and limit DATE: 17/05/25 10:57:36 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov Jan Štrobl, René Hudec and Martin Jelínek (ASÚ CAS, Ondřejov, CZ) We observed the location of the recently discovered GRB 170524A (Gropp et al., GCNC 21135) with the 0.5m robotic telescope D50 located in Ondřejov, Czech Republic. The unfiltered CCD observations started 4 hours after the trigger, once the position got available above local horizon, and had to be interrupted after 20 minutes because of passing clouds. The sum of all images obtained has a mean exposure time 00:02:23UT, i.e. 4.22h after the GRB, and a limiting magnitude of R>20.2. No object was detected within the XRT errorbox (Evans et al., GCNC 21136).