{
  "bibcode": "2021GCN.30757....1B",
  "body": "S. Belkin (IKI), I. Reva (FAP), A. Kusakin (FAP), A. Pozanenko (IKI), \nN.Pankov (HSE), V. Kim (FAP) report on behalf of GRB-IKI-FuN:\n\nWe observed GRB 210820A (Beardmore et al., GCN 30664) with Zeiss-1000 \ntelescope of Tien Shan Astronomical Observatory starting on Aug. 21 (UT) \n21:32:02.\n\nThe optical afterglow (Beardmore et al., GCN 30664; Lipunov et al., GCN \n30666; Fu et al., GCN 30669; Zhu et al., GCN 30670; Butler et al., GCN \n30672; Strausbaugh et al., GCN 30673; Blazek et al., GCN 30674; Laha et \nal., GCN 30675; LaPorte and Beardmore, GCN 30686; Komesh et al., GCN \n30688; Guelbenzu et al., GCN 30695; Kann et al., GCN 30731) was not \ndetected in the stacked image down to a limiting magnitude of 21.8 in R \nfilter. Preliminary photometry of the field in a stacked image is following.\n\nDate       UT start t-T0    Filter  Exp.  OT  Err. UL(3 sigma)\n                      (mid, days)     (s)\n2021-08-21 21:32:02 1.17659  R      27*90 n/d n/d  21.8\n\nThe photometry is based on nearby USNO-B1.0 stars.\n\nUSNO-B1.0\nRA Dec R2\n01:22:01.52088 +04:35:30.2028 17.48\n01:22:14.95944 +04:43:31.2204 17.89",
  "circularId": 30757,
  "createdOn": 1630689098000,
  "email": "apozanen@iki.rssi.ru",
  "subject": "GRB 210820A: TSHAO optical upper limit",
  "submitter": "Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>",
  "eventId": "GRB 210820A"
}