SkyDome, sun, moon, realistic sky

[J@ckWhiteIII]

Hey,
Is there any possibility to get a REALISTIC skydome where i can have just ONE picture with a sun and a moon so that it doesn't just take the picture and copies it a thousand times to set all of them together to a skydome? And where I can also set a time so I can affect the day/night rythm? This is something that really annoys me and if anybody knows a possibility to get all that (OGRE, whatever) please take the time to reply. Thank you