TITLE: GCN CIRCULAR NUMBER: 30190 SUBJECT: GRB 210610B: RATIR Optical and NIR Observations DATE: 21/06/11 05:42:17 GMT FROM: Rosa Leticia Becerra Godinez at Inst. de Astronoma,UNAM Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 210610B (K.L. Page, et al., GCN 30170 and J.P. Osborne, et al., GCN 30189) with the Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2021/06 11.16 to 2021/06 11.18 UTC (7.91 to 8.38 hours after the BAT trigger), obtaining a total of 0.33 hours exposure in the r and i bands and 0.15 hours exposure in the Z, Y, J, and H bands. For a source within the Swift-XRT error circle, in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following detections and upper limits (3-sigma): r = 18.03 +/- 0.01 i = 17.86 +/- 0.01 Z = 17.65 +/- 0.01 Y = 17.47 +/- 0.02 J = 17.55 +/- 0.03 H = 17.43 +/- 0.03 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. Further observations are planned. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.