TITLE:   GCN CIRCULAR
NUMBER:  23868
SUBJECT: GRB 190204A: SAO RAS optical observations
DATE:    19/02/04 19:02:35 GMT
FROM:    Moskvitin Alexander at SAO RAS  <mosk@sao.ru>

A. S. Moskvitin (SAO RAS)
report on behalf of larger GRB follow-up team.

We observed the field of the GRB 190204A (Lien et al., GCNC #23852)
with the Zeiss-1000 telescope of SAO RAS (+ CCD photometer)
on February, 4, 15:36:17--16:44:07 UT (mid. time 16:10:12).
The observations were carried out in Rc band.

We detected the OT (Lien et al., GCNC #23852; Watson et al.,
GCNC #23861; Kuin & Lien, GCNC #23863)
in the stacked 12 x 300 sec. image.

Preliminary brightness of OT is R = 21.9 +/- 0.1 (T-T0 = 0.4335 d).
The calibrations is based on nearby SDSS stars (Volnova et al.,
GCNC #23867), magnitudes converted with the Lupton 2005 equations.