GCN Circular 16748
S. Schmidl, S. Klose, D. A. Kann, U. Laux, L. Pfeifer, C. Pohl, and H. Meusinger (all TLS Tautenburg) report: We observed the field of GRB 140818B (Swift trigger 609885, Vargas et al., GCN 16709) with the 1.34m Tautenburg Schmidt telescope. Starting at 20:34 UT (1.83 hr after the trigger), we obtained in total 12 x 120s Rc-band images. Observations were obtained at a mean airmass of 1.75. In a stack of all available images, we detect the source reported by Aceituno et al. (GCN 16711). Using USNO-B1 field stars for calibration, we derive a preliminary magnitude (Vega magnitude system) of Rc = 20.9 +/- 0.2, at a midtime of 2.08 hr after the burst. The given magnitude is not corrected for the large Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.73 mag in the direction of the burst (Schlegel et al. 1998).