ANH novel, ch. 6, page 73
"The tridimensional solid screen filled one wall of the vast chamber from floor to ceiling. It showed a million star systems. A tiny portion of the galaxy, but an impressive display nonetheless when exhibited in such a fashion."
ANH novel, ch. 7 . . . Tarkin's speech to Leia:
"This station is the final link in the new-forged Imperial chain which will bind the million systems of the galactic Empire together once and for all."
After Alderaan's destruction, Vader checks the display again. From Chapter 8:
"Vader stared at the motley array of stars displayed on the conference-room map while Tarkin and Admiral Motti conferred nearby. Interestingly, the first use of the most powerful destructive machine ever constructed had seemingly had no influence at all on that map, which in itself represented only a tiny fraction of this section of one modest-sized galaxy.
It would take a microbreakdown of a portion of this map to reveal a slight reduction in spatial mass, caused by the disappearance of Alderaan. Alderaan, with its many cities, farms, factories, and towns -- and traitors, Vader reminded himself.
Despite his advances and intricate technological methods of annihilation, the actions of mankind remained unnoticeable to an uncaring, unimaginably vast universe."