Fort_Master_Gustav
Within the calculations between each ship, they eventually realize that this nebula field is indeed quite large. From the border of the nebula to the center, it will take each ship 2000 km to find each other in sensor range, and perhaps whatever is responsible for the Neutron Star and the other antics of this nebula.
Fortunately, there are times where the ships are able to use the gravitational currents to their advantage and maintain the straight line to the center of the nebula, so the entire long journey - still taking will be accurately tracked. They are now currently at 1950 km to center.
At around 1875 km, the North ship gets a strange visual of a bright red light, all too familiar to what it means. Her light watches over all, even through this vessel, this gaseous vortex that seems to show in the galaxy like a zit in the biological features of any lesser being. If anything, it only strengthens their resolve. This is where they are supposed to be.
Around 1800 km, the gravitational forces begin to gain in strength. It becomes harder to keep in a straight line as to measure the distance to the center, and some smaller, not-so-fastened panels of the ships become ajar from the sheer force of the currents. Nothing threatening the integrity of both ships, just a sign of things to come...
Around that same distance, the South ship detects a sudden gap in current just ahead of it, like an invisible tunnel that will not tear apart the ship while it is in its boundaries. This is very curious, and could mean many different things. One of those things being that the South ship could traverse it without risk, but the way this tunnel rotates is faster than the North ship is able to keep up, as there isn't such a tunnel that the North ship could take advantage of. This also means that the straight line will no longer be maintained, and the distance estimate requiring more complex calculation, which in turn might lead to inaccuracies.
Risk and reward... though one other question arises: Why the asymmetry?