GCN Circular 4440
N. Zimmerman, S. Tyagi, & J. P. Halpern (Columbia U.) report: "Using the MDM 2.4m outfitted with RETROCAM, we have obtained an upper limit on the SDSS r-band magnitude of GRB 060105 as of Jan. 6 02:00 UT, or 19 hours after the burst. The sum of eight 5-minute exposures reveals no new source within the refined XRT error circle (Godet et al,. GCN 4433) to a limit of r = 21.0, as calibrated with Sloan standard stars."