Blender 2.8 rotate array in cirle

Hi guys, I still have no good solution on how to create an array modifier for an object to

  1. Rotate in a circle (I know it can be done with an empty that is rotated) but… (see 2)

  2. The objects should keep a certain rotation along a plane like this:

So for example where the 3d cursor is there could be an empty with the same rotation as the cube , then rotate the empty around the local z axis… will work.

The only thing is now: Let’s assume that I have 10 array items. What is the exact rotation of the empty (x, y, z) to create a perfect circle? Because I want to define this programmatically with Python.

Probably not a good idea, however for now you could have presets for 2 to 10 objects.