TITLE: GCN CIRCULAR NUMBER: 27860 SUBJECT: GRB 200528A: CAHA Upper Limit DATE: 20/05/29 22:44:01 GMT FROM: Alexander Kann at IAA-CSIC D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), M. Blazek, C. C. Thoene, J. F. Agui Fernandez (all HETH/IAA-CSIC), and I. Hermelo (CAHA) report: We observed the XRT error circle (Evans et al., GCN #27836) of the bright GRB 200528A (Swift detection: Ambrosi et al., GCN #27832; Fermi GBM detection: The Fermi GBM team, GCN #27831) with the 2.2m telescope at CAHA (Almeria, Spain), equipped with the CAFOS detector. We obtained 21 x 180 s exposures in the Ic band under adverse observing conditions (moonlight, bad seeing and transparency). At the enhanced XRT position, we detect no source (but would have preferred to). We derive a 3 sigma limiting magnitude of Ic > 23.5 mag (Vega) at 0.440865 days after the GRB, calibrated against SDSS standard stars transformed to the Ic band following Lupton (2005). This limit is comparable to those achieved by NOT about an hour later (Malesani et al., GCN #27842).