According to http://en.wikipedia.org/wiki/Apparent_magnitude" [Broken] Neptune could be visible to the naked eye. Neptune's maximum brightness is magnitude 7.78 while the faintest star known to be observed with the naked eye is magnitude 7.72. But that star was only observed as a guide to observe the galaxy M81 by the naked eye by Brian skiff. So, it is not a hard limit at all. http://www.skyandtelescope.com/resources/darksky/3304011.html" [Broken] So, it seems to me that Neptune is just within reach of the naked eye. However, it seems that no one has actually seen it with the naked eye. Why not?