TITLE: GCN CIRCULAR NUMBER: 30128 SUBJECT: Fermi GRB 210605A: Global MASTER-Net observations report DATE: 21/06/05 05:32:21 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210605A ( Fermi GBM team, GCN 30127) errorbox 571 sec after notice time and 600 sec after trigger time at 2021-06-05 05:18:58 UT, with upper limit up to 17.2 mag. The observations began at zenith distance = 86 deg. The sun altitude is -76.8 deg. The galactic latitude b = -74 deg., longitude l = 277 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1628580 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 661 | 2021-06-05 05:18:58 | MASTER-OAFA | (01h 24m 45.07s , -42d 19m 00.9s) | C | 120 | 17.0 | 1023 | 2021-06-05 05:24:31 | MASTER-OAFA | (01h 24m 38.95s , -42d 20m 23.9s) | C | 180 | 17.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.