Adv Camera) Spheres look like eggs???

I am using the advanced camera God tracking mode for a project. When you go by a planet which are just spheres, they start to look as if they are eggs as they approach the edges of the screen. This doesn't happen with the regular camera. Is there a way to counteract this?

Here's a screen shot for reference: http://i56.photobucket.com/albums/g177/burtstanton/g.png

Thanks in advance