This guy ^, knows his stuff.
But the last thing I want to see is a "light in the dark" situation. When I said asteroid, I didn't really mean the ones we come across in combat, rather the huge mammoth ones. What I would expect upon jumping into a system would be this:
A complete planetary map of the system, barring afore mentioned anomalies. I would not expect to able able to see where all th stations are, unless they have a becon (the pros and cons of slapping a becon on a station in a pirate ridden system is debatable). As for fleets, I'm not so sure.
I would certainly expect to be able to see the larger fleets, but perhaps nots the teeny tiny ones. But I also wouldn't want them to be able to creep up on you, unless you're in a nebula or something. That said, it wouldn't be opposed to the smaller fleets not appearing on the system map, and only being visible when they are within the range of your more sensitive sensors.
This could also open up the possibility of something like 'super-duper advanced sensors' that enables something like sonar.