GCN Circular 9762
K. Wiersema (Leicester), D. Malesani (DARK/NBI), A. Levan, D. Steeghs, L. van Spaandonk (Warwick) report on behalf of a larger collaboration: We observed the field of GRB 090809 (Markwardt et al. GCN 9754) with the William Herschel Telescope using the ACAM instrument. Observations consisted of 4 x 300 second exposures with a sloan i filter, starting on August 9, 23:41 UT (6.16 hrs after burst). We clearly detect the afterglow (Markwardt et al. GCN 9754, Xu et al. GCN 9755) with i = 20.48 +/- 0.03 (calibrated using SDSS stars).