Neptune can not be seen with naked eye alone , since Neptune 's normal brightness are between magnitudes +7.7 and +8.0 , which can be out-shined by Jupiter 's Galilean moons , the dwarf planet Ceres , and the asteroids 4 Vesta , 2 Pallas , 7 Iris , 3 Juno and 6 Hebe . Neptune is never visible to the naked eye , having a brightness between magnitudes +7.7 and +8.0 , which can be outshone by Jupiter 's Galilean moons , the dwarf planet Ceres and the asteroids 4 Vesta , 2 Pallas , 7 Iris , 3 Juno and 6 Hebe .