TITLE: GCN CIRCULAR NUMBER: 29779 SUBJECT: Fermi GRB 210410A: Global MASTER-Net observations report DATE: 21/04/10 01:30:12 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210410A ( Fermi GBM team, GCN 29777) errorbox 42 sec after notice time and 69 sec after trigger time at 2021-04-10 00:54:26 UT, with upper limit up to 16.8 mag. The observations began at zenith distance = 85 deg. The sun altitude is -50.6 deg. MASTER-Tavrida robotic telescope located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210410A errorbox 112 sec after notice time and 139 sec after trigger time at 2021-04-10 00:55:36 UT, with upper limit up to 19.1 mag. The observations began at zenith distance = 15 deg. The sun altitude is -22.5 deg. The galactic latitude b = 29 deg., longitude l = 74 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1588428 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 75 | 2021-04-10 00:54:26 | MASTER-SAAO | (17h 48m 53.00s , +47d 14m 34.0s) | C | 10 | 16.4 | 110 | 2021-04-10 00:54:56 | MASTER-SAAO | (17h 48m 58.82s , +47d 13m 30.3s) | C | 20 | 16.8 | 155 | 2021-04-10 00:55:36 | MASTER-Tavrida | (17h 47m 38.38s , +48d 29m 25.0s) | C | 30 | 18.4 | 209 | 2021-04-10 00:56:25 | MASTER-Tavrida | (17h 47m 31.30s , +48d 28m 35.5s) | C | 40 | 18.5 | 666 | 2021-04-10 01:03:22 | MASTER-Tavrida | (17h 54m 11.52s , +47d 16m 38.2s) | C | 120 | 19.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.