FAQ

Half of the green inner gimbal on the prototype seems useless, why is it like this?

The redundant half of the green inner gimbal acts as a counter weight to balance the mechanism.  The weight of the blue tracking surface gimbal is taken on the inner gimbal outer axis, so given the orientation of the prototype, without the counter balances the 3 tracking surface gimbals would produce a torque about the axis of the base mounting shaft.