TITLE: GCN CIRCULAR NUMBER: 17632 SUBJECT: GRB 150323C: RATIR Optical Afterglow Observations DATE: 15/03/24 06:49:44 GMT FROM: Owen Littlejohns at Az State U Alan M. Watson (UNAM), Owen Littlejohns (ASU), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja (GSFC), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of GRB 150323C (Amaral-Rogers, et al., GCN 17621) 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 2015/03 24.14 to 2015/03 24.27 UTC (10.20 to 13.42 hours after the BAT trigger), obtaining a total of 2.49 hours exposure in the r, i and z bands. For a source within the Swift-XRT error circle (D'Elia, et al., GCN 17630), in comparison with the SDSS DR9, we obtain the following detections and upper limit (3-sigma): r 23.00 +/- 0.15 i 22.63 +/- 0.11 z > 20.61 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. In comparison to an earlier epoch of observations (Xin, et al., GCN 17631) we find this magnitude to be consistent with a power-law decay with an approximate temporal decay index alpha = 0.5. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.