Spherical skybox

Hey, I’m having trouble with the spherical skybox. I used this page (http://www.hub.jmonkeyengine.org/wiki/doku.php/jme3:advanced:sky) and the belonging texture but it gets stretched.

I am using the nightly builds.

Also, is there some documentation on how to implement by own post processing shader? Or should I just browse through the source of another?

Greetings and thanks,