TITLE: GCN CIRCULAR NUMBER: 29915 SUBJECT: Swift GRB210430.45: Global MASTER-Net observations report DATE: 21/04/30 17:40:26 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB210430.45 (trigger No 1046014,03h 48m 43.00s , +45d 03m 31.0s, R=0.05) errorbox 12785 sec after notice time and 24452 sec after trigger time at 2021-04-30 17:29:42 UT, with upper limit up to 18.0 mag. Observations started at twilight. The observations began at zenith distance = 70 deg. The sun altitude is -13.5 deg. The galactic latitude b = -7 deg., longitude l = 153 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1604591 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 24543 | MASTER-Kislovodsk | C | 180 | 17.4 | 24543 | MASTER-Kislovodsk | C | 180 | 17.8 | 24823 | MASTER-Kislovodsk | C | 180 | 18.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.