GRB 210330A: MASTER optical observation

MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010, Advances in Astronomy,2010,30L) started GECAM GRB 210330A (D.Y.Guo et al. GCN 29739, Ttrigger=12:45:46.600 UTC, R.A.Dec.: 164.3d,-55.6d, er.-b.=5.1d) optical observations at MASTER-SAAO (located in South African Astronomical Observatory) 17496 sec after trigger time at 2021-03-30 17:37:23 UT at sunset, with upper limit up to 18.7 mag. Observations started at zenith distance = 43 deg. The sun altitude was -13.6 deg. The galactic latitude b = 4 deg., longitude l = 288 deg. Real time updated cover map and OT,that can be discovered, will be available here: https://master.sai.msu.ru/site/master2/observ.php?id=1580304 There are the following upper limits of the first images Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 17587 | 2021-03-30 17:37:23 | MASTER-SAAO | (10h 57m 26.66s , -55d 35m 44.3s) | C | 180 | 18.7 | 17787 | 2021-03-30 17:40:43 | MASTER-SAAO | (10h 57m 26.36s , -55d 34m 44.9s) | C | 180 | 18.6 | 17986 | 2021-03-30 17:44:02 | MASTER-SAAO | (11h 05m 32.80s , -55d 35m 42.8s) | C | 180 | 18.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.