TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3312 SUBJECT: GRB 050416: Optical/NIR observations DATE: 05/04/22 02:16:20 GMT FROM: Paul Price at IfA,UH P.A. Price (IfA), T. Minezaki (U. Tokyo), L. Cowie (IfA) and Y. Yoshii (U. Tokyo) report on behalf of the UH-MAGNUM GRB collaboration: We observed the optical afterglow of GRB 050416 (Cenko & Fox, GCN #3265) with the automated MAGNUM telescope + MIP dual-beam optical-NIR imager, commencing at April 16.53 UTC. The observations were performed in poor seeing with clouds which prevented detection in the I and K bands. Nevertheless, we detected the afterglow in the R, J and H bands. Based on comparison with a single USNO-B1 star, we estimate that the optical afterglow was about R ~ 21.3 mag at the epoch of our observations. This message may be cited.