If you want to use a sky- cube, scene, dome or cylinder -> add the SKY flag to it.

Anyway, you want to move/scale a sky object? Perhaps as a SCENE?
Iirc you can change sky objects in functions lateron:

function blablabla()
{
...
skySphere.scale_x = 5;
}

But dont quote me on this, never tried it except for hiding and showing sky objects.