"Satellite finder uses a lookup data table of magnetic declinations derived from a NOAA declination predictor program named Geomag"
Not sure if that is what you were looking for Wejones, I spent some time on the Geomag site, it is very interesting. I learned the earth's magnetic field is constantly changing and almost impossible to predict....despite that fact, they use the above mentioned predictor program. So apparently, space and time play a large role. Your compass may not point to exactly the same direction today as it will tomorrow
I don't know why the declination values are different from sat finder program to sat finder program. For pointing a dish to a satellite with a compass, accuracy isn't paramount, but lilke you mentioned it seems odd that there would be different values floating around.