> The human eye is able to adapt to very different brightnesses as
> Venus (mag -4) and weak stars (mag 6); that represents a difference
> of 10 mag, that is to say a brightness ratio of 10,000. A computer's
> display is only able to give 256 levels of brightness. So it is
> impossible to render the stars' brightnesses in a so-called
> "realistic way".

If you divide those 256 brightness levels evenly across a 10
magnitude range, you'll get one brightness level for every 0.04
magnitudes! Skilled visual observers are able to distinguish
brightness differences of 0.1 magnitudes....

Therefore, those 256 brightness levels are in themselves no obstacle
against reproducing a magnitude range of 10 magnitudes.

Finally: many modern graphics cards have more than 256 brightness
levels. And most computer displays today are analog devices, i.e.
they have no limit of 256 brightness levels.