TITLE: GCN CIRCULAR NUMBER: 22617 SUBJECT: GRB 180402A: ISON-NM early optical limits DATE: 18/04/08 20:40:42 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), L. Elenin (KIAM), A. Pozanenko (IKI), A. Volnova (IKI), I. Molotov (KIAM) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift short burst GRB 180402A (Lien et al., GCN 22580) with 0.4-m telescope of ISON-NM observatory starting on Apr., 02 (UT) 09:45:39, i.e. 40 seconds after the burst trigger. We obtained 4 unfiltered images of 30 s exposure each. We do not detect any source within XRT error circle (Lien et al., GCN 22580). Upper limits are following. Date start (Ut) t-T0 Exp. UL (3sigma) (mid.,sec) (s) 2018-04-02 09:45:39 55 1*30 14.5 2018-04-02 09:45:39 133 4*30 15.0 The photometry is based on nearby USNO-B1.0 stars (R2 magnitudes).