The Lunar Reconnaissance Orbiter (LRO) is a nice S-Band (2271 MHz) signal coming from the moon to calibrate your dish. This is especially helpful if you need the accuracy for even higher frequencies where the beam-width is narrower. Below is a screenshot after optimization of LNA assembly, calibration of azimuth and elevation as well as adjustment of phase center of the feed.
The LNA assembly and feed shown below is just temporary for this measurement. Normally the LNA is located a few meters away inside an equipment box but for this peaking i wanted to remove all feed line loss.