TITLE:   GCN CIRCULAR
NUMBER:  29809
SUBJECT: GRB 210411C: Chilescope optical observations
DATE:    21/04/12 20:40:48 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), M. Krugov (AFIF), N. Pankov (HSE) 
report on behalf of IKI-FuN follow-up collaboration:

We observed the Swift GRB 210411C (Sbarrato et al., GCN 29794) with 
Chilescope RC-1000 started on April 12 (UT) 07:43:39 in r'-filter. We 
clearly detected optical afterglow (Sbarrato et al., GCN 29794; 
Strausbaugh et al., GCN 29802; Hu et al., GCN 29803; Lipunov et al., GCN 
29804; de Ugarte Postigo et al., GCN 29806; Pessi et al., GCN 29808) in 
a stacked image with a total exposure of 3*600 seconds.

Preliminary photometry is following.

Date       UT start   t-T0       Filter Exp.   OT    Err.  UL(3sigma)
                      (mid, days)        (s)
2021-04-12 07:43:39   0.70333    r'     3*600  21.76 0.16  22.4

The photometry is based on nearby stars from the SkyMapper catalog
SMSS-DR1.1_id r
194633.88-392221.5 17.428
194648.73-392400.2 16.180