Orientation relative to orbiting body ?

[pixartist]

I know I can use

Program.Vessel.VesselSAS.LockHeading(); to set the heading of the SAS. Now what exactly is the relationship between the Euler Angles used to construct the quaternion for the SAS heading and the actual position on the navball ? Are they relative to world space or to the body my vessel is orbiting ? What's the most elegant way to use the three values of an euler angle to set the pitch (x), yaw(y) and roll(z) relative to the object I am orbiting ? Is there maybe some "navball quaternion" which I could use to rotate my constructed quat to the correct orientation ? Thanks