We also estimate limiting magnitudes for the , , and bands using the images of M67. The measured sky brightnesses in , , and were , , and , respectively. For each band, images were obtained with dithering. We note that we used a high speed readout mode (2 MHz). We apply bias-flat correction and stellar position alignment to the data and stacked them into a single image for each band. We conduct photometry for stars on each stacked image by using the DoPHOT package,24 which performs an analytical PSF fitting. The measured instrumental magnitudes of these stars were then compared to the SDSS 9 catalog25 for photometric calibration. We note that we here ignore color terms and simply approximate that the , , and bands are identical to the , , and bands, respectively. Limiting magnitudes with 10-min exposures are estimated as the signal-to-noise (S/N) ratio reaches 10, yielding , , and . We note that is affected by higher readout noises in band (see Table 1) as we used the high speed readout mode. For the S/N calculation, we simply adopt the photometric errors returned by DoPHOT. We show a plot for SDSS magnitudes versus photometric errors in Fig. 19.