TITLE: GCN CIRCULAR NUMBER: 36168 SUBJECT: GRB 240418A: TSHAO Zeiss-1000 optical upper limit DATE: 24/04/19 01:36:41 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Pozanenko (IKI), I. Reva (FAI), N.Pankov (HSE), S. Belkin (IKI) report on behalf of GRB-IKI-FuN: We have observed the field of GRB 240418A (Siegel et al., GCN 36162) with Zeiss-1000 telescope of Tien Shan Astronomical Observatory starting on 2024-04-18 (UT) 21:47:25. We do not detect any object within Enhanced Swift-XRT position (Evans et al., GCN 36166) up to R=21.6. Preliminary photometry of the field in a stacked image is following. Date UT start t-T0 Filter Exp. OT Err. UL(3 sigma) (mid, days) (s) 2024-04-18 21:47:25 - R 21*120 n/d n/d 21.6 The photometry is based on nearby USNO-B1.0 stars. Non detection of the OT is in agreement with the observations (Lipunov et al., GCN 36163; Odeh et al., GCN 36165; Malesani et al., GCN 36167).