GRB 230427A: Bassano Bresciano Observatory upper limit

We imaged the field of GRB 230427A detected by SWIFT(trigger 1165948) with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy. Member of: AAVSO - American Association of Variable Star Observers. UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili. GAC - Gruppo Astrofili Cremonesi. The observations started 8.72 hour after the GRB trigger, at the end of twilight, with our Newton telescope D=250 mm F/D=4.8. Weather conditions were good. We co-added 2 series of 25 exposures of 60 sec each. Start T0+ End T0+ Rlim 8.72 hour 9.63 hour 19.5 We did not found any optical counterpart in the error box of the XRTcandidate. Troja et al., GCN 33687 Magnitudes were estimated with the USNO-B1.0 cat. and are not corrected for galactic dust extinction. Reference: http://www.osservatoriobassano.org/GRB.asp The message may be cited.