TITLE: GCN CIRCULAR NUMBER: 21293 SUBJECT: GRB 170705A: RATIR Optical and NIR Observations DATE: 17/07/05 14:58:02 GMT FROM: Nat Butler at Az State U Nat Butler (ASU), Alan M. Watson (UNAM), 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 (ASU), and Vicki Toy (UMD) report: We observed the field of GRB 170705A (Starling, et al., GCN 21289) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2017/07 5.17 to 2017/07 5.26 UTC (1.34 to 3.41 hours after the BAT trigger), obtaining a total of 1.42 hours exposure in the r and i bands and 0.59 hours exposure in the Z, Y, J, and H bands. We detect the optical transient found by Swift and observed MASTER-OAFA (Lipunov, et al., GCN 21291). In comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following detections: r = 18.60 +/- 0.01 i = 18.30 +/- 0.01 Z = 18.03 +/- 0.01 Y = 17.79 +/- 0.01 J = 17.79 +/- 0.01 H = 17.56 +/- 0.01 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The source fades as in time as t^(-0.4) during our observation. We note that the Swift-UVOT detection makes this GRB unlikely to be at very high redshift. Our photo-z calculations, using RATIR data alone, suggest z<4. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.