Hey all, brand-new here myself and this is my first post. Be honoured B)
I was under the impression that skybox and sky sphere (I'll use the term "sky dome" in this post) are two different technologies.
A sky dome is actual geometry that surrounds a level. Therefore, you either end up with a lot of polygons in your sphere or really large geometry that shows seams, especially if you use a cube.
A skybox is when you have a separate area in a map--like a little room--with only a camera and the sky elements in it. When the player's camera rotates, so too does the camera in the skybox. The view in the skybox is composited with the view from the level--just added into the background. That way the player will never bump up against the geometry that makes up the sky dome, only against the geometry of the level--because there IS no geometry making up the sky, only a masked-in image that's been rendered somewhere else.
That's lifted pretty much verbatim from Luke Ahearn's book 3D GAME TEXTURES.
IMO, you'll get a much better effect--especially for your space sim which requires lots and lots of, well, space--if you use the skybox technique I mentioned here, and not a sky dome or sky sphere.