In this paper, we study the feasibility of a method for vicarious calibration of the GOES Imager visible channel using the Moon. The measured Moon irradiance from 26 undipped moon imagers exhausted all the potential Moon appearances between July 1998 and December 2005, together with the seven scheduled Moon observation data obtained after November 2005, were compared with the USGS lunar model results to estimate the degradation rate of the GOES-10 Imager visible channel. A total of nine methods of determining the space count and identifying lunar pixels were employed in this study to measure the GOES-10 Moon irradiance. Our results show that the selected mean and the masking Moon appears the best method. Eight of the nine resulting degradation rates range from 4.5%/year to 5.0%/year during the nearly nine years of data, which are consistent with most other degradation rates obtained for GOES-10 based on different references. In particular, the degradation rate from the Moon-based calibration (4.5%/year) agrees very well with the MODIS-based calibration (4.4%/year) over the same period, confirming the capability of relative and absolute calibration based on the Moon. Finally, our estimate of lunar calibration precision as applied to GOES-10 is 3.5%.