SunSean If I remember correctly its in the 6-11% range, with an average of around 10% - which was the initial correction applied, but it is a bit more specific now. Basically, the newer Kipp and Zonen automatic sensors have a standard WMO threshold of 120 Wm-2, but the older Campbell stokes manual recorders burned the measuring paper at anywhere from 106-285 Wm-2 (A. Kerr and R. Tabony: 'Comparison of sunshine recorded by Campbell-Stokes and automatic sensors' (Weather, April 2004, vol. 59,90-95).