TITLE: GCN CIRCULAR NUMBER: 44592 SUBJECT: GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation. DATE: 26/05/13 00:24:14 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai@tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 260511B detected by Fermi/GBM (Fermi GBM Team, GCN 44542) and SVOM/ECLAIRs (Godet et al., GCN 44543) with the 14 inches Schmidt-Cassegrain (Celestron 14) telescope F/D=7. The observations were started at 2026-05-11 21:24:23 UT (approximately 10.40 hours after burst) stacking two sets of unfiltered CCD image. The observations were carried out with clear skies and good visibility conditions. The OT was detected at the following position: RA (J2000.0) 12h 50m 17.18s Decl. (J2000.0) +04° 03' 10.2" Photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Mag. err. 2026-05-11 21:54:50 UT 10.91 60x60s CR 18.85 +/-0.04 2026-05-11 23:01:52 UT 12.02 72x60s CR 18.95 +/-0.04 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported Wu et al. (GCN 44547); Sasada et al. (GCN 44549); Jiang et al. (GCN 44551); Wu et al. (GCN 44552); Li et al. (GCN 44557); Vijaykumar et al. (GCN 44561); De Ugarte Postigo et al. (GCN 44565); Lee et al. (GCN 44567); Li et al. (44568); Belkin et al. (GCN 44572); Saccardi et al. (GCN 44574); Rajabov et al. (GCN 44576); Pérez-Fournon et al. (GCN 44577); Novotný et al. (GCN 44580); Moskvitin (GCN 44582). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44592. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...