New to autoguiding (have just emerged from the late Jurassic period

).
I am using a ZWO ASI 120MC camera connected to a HEQ5 Pro with an ST4 cable and the camera also connected to my Laptop via USB. So are the correct settings in PHD2 with my setup the following?
Camera - 'ZWO Camera'
Mount - 'on camera'
Aux Mount - 'none'
Another question, when do you use the Aux Mount option?
Thanks for helping.
RichardJ