How far can a human see at night?
At night you can actually see further than during the day. At night you can see stars that are many light years away, but during the day the furthest thing you can see is probably the sun, which is 8 light minutes away. There's probably no definite answer because the brighter and bigger the object (and the darker the surrounding and the clearer the air), the greater the distance from which you can see it. 

According to Sky and Telescope, the most remote stars (as part of Andromeda Galaxy) you can see with a naked eye are 2.5 millions light years away.

Talking about the objects on earth, at half-moon, you could see to "the end," that is to the horizon.