The net, _one number_ solution for the universe's total integrated star light in visual (V-band) magnitudes which Abdul Ahad calculated as an analytical approximation in July 2004:-
Ahad's constant = (magnitude of stars) + (magnitude of milky way)
= (-6.0) + (-5.1) = -6.5 mags net (1/300th of a Full Moon).
If you added up the minute amounts of light from each and every single star visible across the full, 360-degree spherical celestial sphere around you, the total flux would roughly equate to AC. It is simply the total amount of light an observer would visually experience in local interstellar space, when located away from the bright neighbourhood of our Sun. For a fuller discussion on usenet, see these threads.
The original article (which is rather long) can be accessed here.
In actual practice, stars shining across the night sky will forever remain in their scattered positions across the celestial sphere to which they appear glued, so would it ever be possible to 'roll up' such scattered sources into a single ball of light, as stipulated by Ahad's constant?
If you accept Einstein's theory of Relativity and such like then AC would, at least in theory, become 'real' when travelling at speeds very close to the speed of light!
Universe views at various speeds Edit
The view of the universe from this kind of slow ship looking out in all directions into space will appear pretty normal, just your average star filled sky:
For a starship accelerating upwards to a significant fraction of the velocity of light (299,792.458 km/sec), the entire celestial sphere will be seen to be squeezed into a narrow window of light in the frontal direction of the ship, as shown in figures 1 through 4 below.
The diameter of the circular window will reduce due to distortions in the space/time frame of reference by virtue of Einstein's Special Theory of Relativity. In theory, the rate of decrease in the diameter of this circular window is expected to be governed by the equation of Lorentz contraction, i.e. in the ratio:
[1-(v^2/c^2)]^1/2 : 1
Further, the convergence of the entire universe into a circular dot of light (figure 4 above), whose dimensions are zero and whose flux amounts to Ahad's constant of -6.5 magnitudes, will only be possible at a theoretical ship velocity of exactly 'c'.
As the ship decelerates, the observations will play back in a reverse order, with the starry points of light resuming their scattered state of appearance. For a starship periodically accelerating and decelerating at velocities close to 'c', an observer would experience a kaleidoscopic effect of colour-changing starfields that condense and disperse in the relativistic observation window. This might happen, for example, when the starship is flying through interstellar media of variable density.
Page links here from Abdul Ahad