Celestia Forums

Just wondering, what is the lowest apparent magnitude the human eye can see, a) from the ground assuming good atmospheric conditions, and b) in space (assuming of course that there is something keeping in the atmosphere so your eyeballs don't explode into the vacuum, obviously).

Also, at what apparent magnitude does Celestia draw the flares around the stars?

Atmospheric extinction varies depending on wavelength. It dims blue stars more than red stars, and amounts to a few tenths of a magnitude at the zenith, and around three magnitudes near the horizon, under a clear sky.
With good dark adaptation under a clear sky far from light pollution, you should be able to see down to magnitude 7. With a lot of time, care and the exclusion of all extraneous light, some people have been able to detect stars around magnitude 8, but under far-from-natural conditions.

Grant