GCN Circular 10058
D. A. Perley (UC Berkeley) reports: I observed the location of GRB 091020 (Racusin et al, GCN 10048) starting at UT 2009-10-21 12:30 using the Nickel 40-inch telescope at Lick Observatory. A series of nine exposures in R-band were acquired, followed by five exposures in I-band and an additional sequence in R-band during morning twilight. All exposures except for the first were of 180 seconds duration. The afterglow is marginally detected in individual frames and well-detected in a combined stack. Calibrating relative to five nearby SDSS standard stars transformed to R-band using the transformation equation of Lupton (2005), the estimated magnitude of the afterglow in the first R-band stack is: R = 20.91 +/- 0.13 mag (t_mid = 15.17 hr) Additional follow-up is planned if weather permits.