second "skybox" camera and fps problem

I wanted to make my skybox look like it was moving so I added a second camera that renders only the skybox and made my Main Camera render depth only for everything else. I have the second camera as a child of the Main Camera and a script that spins the second camera. The problem is that when I look in a direction lets say up for an extended period of time when I look back down the skybox is now rotating in the wrong direction. I think this is because I am rotating the second camera with a cameratwo.transform.Rotate(Vector3.up Time.deltaTime speed) and when it is angled up with the Main Camera it's y axis is now at an angle. I have tried to rectify this by changing the Camera's rotation to world space, local space, and have even tried to have it rotate around the players y axis with no luck. I am not very experienced with rotations in unity and am wondering if anyone else has had this same problem or if anyone has a tip about a solution?