I saw this thread about Neptune's naked eye visiblity: https://www.physicsforums.com/showthread.php?t=362668 . I found this thread when I was searching for an answer to the very same question that is asked there. In every source I've seen that actually details the Bortle Dark Sky scale it has been said that one can see down to Mag 8 under perfect conditions (I think I've seen some sources that have said 8.5, which makes this even more puzzling.) Neptune's magnitude is sometimes as bright as 7.78. Yet, every single source I've seen has said that Neptune is not naked-eye visible even under perfect conditions. To be clear here, I do understand the basic issues relating to apparent magnitude and such. I am aware that Neptune is way farther from earth than the naked eye planets, and that that is the reason why it is so dim. But... it seems like according to the Bortle Dark Sky Scale it would be just barely within naked eye range under absolutely perfect conditions. Is this true? I've had trouble finding anything that actually addresses the issue, most of the sources that say you can go down to mag 8 do not address Neptune in particular, while most sources that talk about the naked eye planets just say "Neptune is too dim." So... is it actually possible to see Neptune with the naked eye?