What is with the blotting out the sun thing? That would kill all life on earth.
Remember we're in Tamriel, not planet Earth, and as far as I'm concerned, I'm not looking forward to a sun-less Skyrim. I'm no emo. Dawnguard all the way, but like most people, I'll probably make a new character or 2 separate save games. I'll go see the Dawnguard with my main character, and pay the vampires a visit with my secondary character.
Correct.
There are no sun in the universe. The starts, the moon and the sun are simply Aedras work. It's the way the brain of the mortals sees Aetherius, which is the realm of the Aedra.
So no, blocking out the sun wouldn't do a thing to Tamriel. It would be darker, but that's it.
Magnus was still close to full strength when he fled, and in doing so, punched a hole in the night sky directly through to the Aetherius itself, which mortals see as the sun
Taken from the wiki.