TITLE: GCN CIRCULAR NUMBER: 13198 SUBJECT: GRB 120320A: early optical upper limit DATE: 12/04/03 18:22:28 GMT FROM: Alina Volnova at SAI MSU A.Volnova (SAI MSU),  E. Sinyakov (ISON), D. Varda (ISON), I. Molotov (KIAM),  A. Pozanenko (IKI) on behalf of  larger GRB follow up  collaboration report: We observed the field of the Swift GRB 120320A  (Markwardt  et al., GCN 13071) with ORI-25 (0.25-m) telescope of ISON-Blagoveschensk observatory. We took several unfiltered images of  60 s exposure on Mar.20, starting (UT) 12:06:10, i.e. 10 min after trigger. Within enhanced XRT position (Beardmore et al.,  GCN 13075) we do not detect any  source in different combined images. Photometry is based on nearby USNO-B1.0 stars, R2-values. UT start,    t-t0           filter      Exp.        OT      UL (3 sigma)               (mid, days)             (s) 12:06:10  0.00874    none     10x30       n/d      16.7 12:06:10  0.08435    none   360x30       n/d      19.2