{
  "bibcode": "2021GCN.29894....1P",
  "body": "N. Pankov (HSE, IKI), S. Naroenkov (INASAN), A. Pozanenko (IKI),  S. \nBelkin (IKI), M. Ibrahimov (INASAN)  report  on behalf of IKI GRB FuN:\n\nWe observed the field of  GRB 210420B (Moss et al., GCN 29833; Lien et \nal., GCN 29854; Osborne et al. GCN 29876; Stamatikos et al., GCN29879) \nwith Zeiss-1000 telescope of Koshka observatory (INASAN). We marginally \ndetect the optical afterglow  (Lipunov et al., GCN 29845; Oksanen et \nal., GCN 29846; Hu et al., GCN 29847; Tianrui Sun et al., GCN 29848; \nLeonini et al., GCN 29851; de Ugarte Postigo et al., GCN 29852, 29853; \nWatson et al., GCN 29858; Zheng et al., GCN 29861; Breeveld et al., GCN \n29862; Stecklum et al., GCN 29863; Butler et al.,GCN 29864; Jelinek et \nal., GCN 29866; Watson, GCN 29867; Leonini et al., GCN 29872; Guelbenzu \net al., GCN 29890).\n\nPreliminary photometry of the afterglow is following\n\nDate       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)\n                      (mid, days)        (s)\n2021-04-21  20:02:55    15*180    1.03507 R    21.0   0.3  21.0\n2021-04-22  20:16:45    24*180    2.05405 R     n/d   n/d  20.5\n\n\nThe photometry is based on the nearby USNO-B1.0 stars\nUSNO_B1.0_id R2\n1325-0345119 16.12\n1326-0349499 16.57",
  "circularId": 29894,
  "createdOn": 1619202709000,
  "email": "apozanen@iki.rssi.ru",
  "eventId": "GRB 210420B",
  "subject": "GRB 210420B: Zeiss-1000 of Koshka optical observations",
  "submitter": "Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>"
}