TITLE: GCN CIRCULAR NUMBER: 30824 SUBJECT: Swift GRB 210912A: Global MASTER-Net observations report DATE: 21/09/12 16:40:30 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> 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 GRB 210912A ( E. Troja et al., GCN 30820) errorbox 19826 sec after notice time and 19878 sec after trigger time at 2021-09-12 16:32:29 UT, with upper limit up to 15.0 mag. Observations started at twilight. The observations began at zenith distance = 57 deg. The sun altitude is -12.6 deg. The galactic latitude b = 32 deg., longitude l = 134 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1718486 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 5800 | MASTER- | C | 25 | 13.0 | 8423 | MASTER- | C | 20 | 17.6 | 8423 | MASTER- | C | 20 | 13.9 | 19968 | MASTER-Kislovodsk | C | 180 | 15.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.