Calibrating Ptarmigan array antenna using background sky rather than dummy load

In my previous posts, I calibrated my 1420 MHz radio telescope using a 50 Ohm dummy load. This worked well. However, since Monday, we have been in Italy and day before yesterday I logged into the laptop running this telescope and accidently closed down SDR# software, thereby losing the calibration. As I am not at home, I could not re-calibrate using the 50 Ohm dummy load as this requires me to manually disconnect the antenna array and connect to the dummy load. So, instead, I tried calibration by taking my background reading when the telescope was pointed away from the Milky Way (it points currently at Zenith and Milky Way crosses Zenith in early morning so I took the background reading at 10am when Milky Way had moved away from the Zenith). This seems to have worked well and, if anything, the background calibration appears smoother than with the dummy load.