Rotation angles for Anchors

I am looking to modify my RetinaNet implementation to support arbitrary orientation object detection using satellite images. What are some common rotation angles to use for generating the target anchors?

Some papers I have looked at only cover the range -[pi/2, 0), I would have thought to cover the range of -[2*pi, 0) or at least -[pi, 0) to avoid duplicate anchors.

Any pointers would be greatly appreciated, Thank you!