Remember...the only stupid question is the one not asked.....so it looks like you're a pretty smart fellow lol..

You don't need a transparent sky in order to achieve this. Go into the atmosphere editor and under effects, unclick the stars.

Now, you can take a photo of stars, galaxies, etc from Hubble or make your own starfield in photoshop and place it on an alpha plane in the first panel, then place it again in the second panel. Click the little 'invert' button to the top right of that second panel and place your alpha plane way huge in the sky. Then, in the material editor under 'effects', raise the luminosity and diffuse till it's bright enough.

Check out Silverblade's tutorials at his site.....(I'm at work and can't switch to give you the link so just find his name in the forum here and click on it.)