Losing Shape with Polygon Collider 2D

Hi,

When I'm using Polygon Collider 2D and rotating an object, the collider shape does not stick with my image, see below:



Top pic is my tweaked Polygon Collider 2D shape, second pic is what Polygon Collider 2D shape looks like after about 60 - 90 degrees of rotation, what am I doing wrong?

Here is the code for rotating the asteroid:

Code (csharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4. public class Rotate_Object : MonoBehaviour {
5. public float RotationSpeed;
6. // Use this for initialization
7. void Start () {
8. }
9. // Update is called once per frame
10. void Update () {
11. transform.Rotate(new Vector3(0,0,Time.deltaTime * RotationSpeed));
12. }
13. }
14.  
15.  

 

Any ideas?

 

Also, this asteroid is contained in another 2d quad that is blank, the quad in moving linearly...

So in other words, I have a quad moving in a straight line, then this asteroid 2d quad underneath it rotating. Still can't see why the Polygon Collider 2D doesn't appear to rotate at the same angular velocity as the 2d sprite?