TITLE:   GCN CIRCULAR
NUMBER:  34516
SUBJECT: GRB 230812B: SAO RAS RC-500 and Zeiss-1000 observations
DATE:    23/08/21 19:58:42 GMT
FROM:    Moskvitin Alexander at SAO RAS <mosk@sao.ru>

A. S. Moskvitin, V. V. Vlasyuk (SAO RAS), V. P. Goranskij (SAI MSU),
report on behalf of the GRB follow-up team.

We observed the field of GRB 230812B (Fermi GBM Team, GCN 34386;
Scotton et al., GCN 34392; Page et al. GCN 34394; Kuin et al.,
GCN 34399; Casentini et al., GCN 34402) with the SAO RAS optical
telescopes RC-500 and Zeiss-1000 equipped with the CCD photometers.
We obtained 90 x 60 sec. images in Rc band with the 0.5-m telescope
on August 20, 18:36:51--20:27:56 and 6 x 300 sec. images in Rc band
with the 1-m telescope on August 20, 21:09:05--21:43:00 UT.

The OT (Lesage et al., GCN 34387; Scotton et al., GCN 34392; Page,
GCN 34394; Zheng & Filippenko, GCN 34395; Lipunov et al., GCN 34396;
Salgundi et al., GCN 34397; Ackley et al., GCN 34398; Xiong et al.,
GCN 34401; Casentini et al., GCN 34402; Frederiks et al., GCN 34403;
Mao et al., GCN 34404; Odeh et al., GCN 34405; Moskvitin & Spiridonova,
GCN 34406; Leonini et al., GCN 34408; de Ugarte Postigo et al.,
GCNs 24409, 34410; Belkin et al. GCN 34412; Ruocco et al. GCN 34413;
Frederiks et al. GCN 34414; Ruocco et al. GCN 34415; Shrestha et al.
GCN 34416; Quadri et al. GCN 34417; Adami et al. GCN 34418;
Moretti et al. GCN 34419; Kumar et al. GCN 34420; Belkin et al. GCNs
34421, GCN 34423; Pyshna et al., GCN 34425; Moskvitin & Spiridonova,
GCN 34428; Quadri & Strabla, GCN 34430; Mihov et al., GCN 34431;
Belkin et al. GCN 34432; Klose et al., GCN 34435; Scarfi, GCN 34436;
Moskvitin & Spiridonova, GCNs 34442, 34461, 34471, 34475;
Vinko et al., GCN 34463; H. Kumar et al., GCN 34500; Turpin et al.,
GCN 34508) is clearly detected in our stacked frames
with the brightness of R = 21.58 +/- 0.11 (t_mid - t0 = 8.0237 days)
and R = 21.44 +/- 0.07 (t_mid - t0 = 8.1027 days).

This preliminary photometry is based on the nearby SDSS stars;
magnitudes are converted using Lupton (2005) equations.