TITLE: GCN CIRCULAR NUMBER: 37995 SUBJECT: GRB 241030B: BTA observations DATE: 24/10/31 00:19:17 GMT FROM: Moskvitin Alexander at SAO RAS A. S. Moskvitin, A. S. Vinokurov (SAO RAS), A. S. Pozanenko (IKI), N. Pankov (IKI, HSE) report on behalf of the GRB follow-up team. We observed the field of GRB 241030B (Fermi GBM team, GCN 37980; Klingler et al., GCN 37981; Evans, GCN 37983; Zhao et al., GCN 37984; Evans et al., GCN 37992), with the 6-m telescope of SAO RAS equipped with the focal reducer Scorpio-I. We obtained quasi-simultaneous 16 x 30 sec images both in B and Rc bands on October 30. The OT (Fu et al., GCN 37985; Odeh et al., GCN 37986; Brivio et al., GCN 37991; Moskvitin t al., GCN 37987) is clearly detected in the Rc stacked frame, but not presented in the B stacked frame: UT_start--UT_end t_mid - T0, h filter OT_mag limit (3sigma) 20:17:39--20:43:25 1.9367 R 22.10 +/- 0.08 24.0 20:18:28--20:44:15 1.9504 B n/d 24.0 This preliminary photometry is based on nearby PS1 stars (magnitudes converted with Lupton 2005 equations) and not corrected for the Galaxy extinction. We also obtained 2 x 1200 sec spectrum with VPHG550G grism (3500--7500 AA, FWHM resolution ~ 10A) on October 30, 19:34:07--20:14:23 UT (T-mid - T0 = 1.3319 hours). In the spectrum we do not find a continuum lower than 5200A. Due to non-detection in B filter and absence of continuum we conclude that redshift of the GRB z >~ 3.3.