There are 3 main calibrators that we can use to obtain the telescope offsets. They are the standard WSRT calibrators 3C147, 3C48 and 3C286. They can be used at both wavelengths.
The scan file from the calibrator source contains the telescope gain and phase offset. These offsets have to be transferred to the scan file of the object. Before the offsets are transferred, please check the Hour Angle range of the calibrator observation in order to find out whether we need to delete some shadowed data.