Will be testing out a new auto panning head and I am used to seeing Diagonal Angle of View, for the Canon 50mm f1.4 this is 46 degrees.
Never had to worrk about this with my manual head as I aligned by eye.
Edit: I think I have just answered my own question. The product documentation was not that clear, but when I turned the controller on it asked for both the Horizontal and Vertical Fields of view in degrees. So now I can figure out the FOV's for the lenses I use, and for the Canon 50mm f1.4 the Horizontal FOV is 39.6 degrees, the vertical FOV is 27 degrees and the Diagonal FOV is 46.8 degrees.