GCN Circular 9244
M. Im, C. Choi, Y. Jeon, W. Park, I. Lee (Seoul National Univ), Y.-B. Jeon (KASI) and Y. Urata (NCU) on behalf of EAFON team. We took a series of Y-band images of GRB090423 using the 1.0m telescope at Mt. Lemmon (Arizona, US) operated by the Korea Astronomy Space Science Institute. We do not detect the afterglow in a stacked image with the total exposure time of 78 min, placing an upper limit of Y < 19.8 (Vega) at 3-sigma at the mid point of UT April 24, 06:16. The photometry calibration was done using the calibration data reported in Im et al. (GCN 9242, 9221). We thank the LOAO operator, J. Yoon for his assistance for this observation.