TITLE:   GCN CIRCULAR
NUMBER:  37922
SUBJECT: GRB 241026A: BTA and Zeiss-1000 optical observations
DATE:    24/10/28 02:29:19 GMT
FROM:    Moskvitin Alexander at SAO RAS <mosk@sao.ru>

A. S. Moskvitin, A. S. Vinokurov, O. I. Spiridonova (SAO RAS),
A. S. Pozanenko (IKI) report on behalf of the GRB follow-up team.

We observed the field of GRB 241026A (The Fermi GBM team, GCN 37894;
Melandri et al., GCN 37896, Li et al., GCN 37909) with the BTA,
6-m telescope of SAO RAS (equipped with the focal reducer Scorpio-I
and V, Rc filters) and also with the 1-m telescope of SAO RAS,
Zeiss-1000 (equipped with the CCD-photometer and Rc filter)
on October 27.

The OT (Moskvitin et al., GCNs 37899, 37916; Watson et al., GCN 37900;
Zheng & Filippenko GCN 37903; Shrestha et al., GCN 37913; Mo et al.,
GCN 37915; Mohan et al., GCN 37918) is clearly detected in our stacked
frames with the following brightness:

UT_start--UT_end   t_mid-T0  exp, s  R magnitude     R_lim  telescope
18:37:41--18:41:24 0.8313 d  4 x 20  21.24 +/- 0.09  23.7   BTA
18:47:40--19:31:31 0.8521 d  8 x 300 21.23 +/- 0.11  23.8   Zeiss-1000

The frames were calibrated against nearby USNO-B1 stars
(R2 magnitudes) and not corrected for MW extinction.