TITLE: GCN CIRCULAR NUMBER: 12388 SUBJECT: GRB110918A: Lick Observations DATE: 11/09/23 01:36:34 GMT FROM: Daniel Perley at U.C. Berkeley D. A. Perley (Caltech), M. Ganeshalingam, P. Blanchard, and M. Mason (UC Berkeley) report: We observed the location of bright IPN GRB 110918A (Hurley et al, GCN 12357) starting at UT 2011-09-22 03:04:29 UT using the Nickel 40-inch telescope at Lick Observatory, under good seeing conditions at high airmass. A series of five 180-second exposures in R-band were acquired in total. The optical afterglow (Tanvir et al., GCN 12365) is well-detected in the combined stack. Using five nearby USNOB1.0 stars, we calculate the following photometry: R = 20.68 +/- 0.13 (t_mid = 3.2406 day) The uncertainty estimate does not include the uncertainty of the calibration to USNO (for convenience, our calibration stars are listed below). The measurement indicates a decay slope of approximately alpha=2.2 since the report of Guidorzi et al. (GCN 12382) and may suggest a very early jet break for this burst (see also Cenko et al., GCN 12367). USNO calibration stars: RA dec R2 032.546809 -27.104117 19.38 032.549492 -27.121698 19.29 032.555214 -27.117650 19.38 032.558045 -27.100853 19.39 032.569403 -27.106270 19.40