I noticed when mapping a ship's destination through an unexplored area that the path jigged about to avoid objects that were invisible to me. This at least occurred with the new nebulae fields thingie. Didn't test to see if it was avoiding planets or asteroids as well.
So...paths through an unexplored area should always be straight and thus blind to the player. Stop the ship if it runs into ANYTHING.
Alternatively or additionally, I'm thinking nebulae fields at even fairly far distances should be exposed to a player once a ship has LOS to it.
--David