I like the idea of a self-revealing map, but mostly for named objects. A ship entering a sector should know about any nebulae, black holes, and asteroids immediately. These things are visible far away, even from Earth. And obviously the players should know about any stations or friendly ships in the sector.
Mines, monsters, space whales, enemy ships, and anomalies could be revealed as they go.
"Damn the torpedoes! Four bells, Captain Drayton!"
(Likely actual words of Admiral David Farragut, USN, at the battle of Mobile Bay. Four bells was the signal for the engine room to make full steam ahead).