I was following this short tutorial about creating a planet by warping a grid or plane. It works great, but I'm having one problem: the polar ends of the planet (top and bottom) are sort of coming together in a point. It's really distorted. Here's a picture.
Here's one of my nodes and UV map.
I'm not sure if it's the texture, because everyone else was using Earth textures and I made my own in Gimp. Is there a way to fix this?