I suppose your method could possible work NewBlack but actually it's as Gibmaker says. The images are pre-rendered and with some coding they can be made to rotate.
Thanks to the both of you for the comments/interest =]
Cut a hole in the sky background, move a rolled-out map of the planet move "across" the hole on a layer under the sky-with-round-hole-in... I guess? you could use some semi-transparent black on another picture to add shadow to create roundness.