Paul was handicapped. The spotter was not available. Lacking the spotter to use as a point of aim, Paul was forced to choose the aiming telescope in the dome instead of the more precise cross-hairs on the optical-glass. This added to the error, and to add once more to that error was the fact that spacecraft in flight tend to revolve along their driving axis so that the angle between the true line of flight and the aiming point changed in angle. Paul would have to use Alpha Centauri itself as a point-of-aim. The correction-angle was supplied by the observatory, and applied to the aiming telescope in the dome.
A lot of minute errors that added up to a gross at the end of flight. Basically, the job of the galactic survey would remove one of the errors: That of the crude measurement of distance between the stars themselves.
Paul was a good pilot. He cut the aiming-star close and watched it in the 'scope until it disappeared. He was now in that blackness that surrounded every ship during the faster-than-light speed. He was on his way. Nothing to do for two weeks but wait for the course to end. Nothing to do but to sit and think, and plan, and dream. To think of Haedaecker and the Z-wave; to plan for the future when his discoveries brought him fame and fortune; to dream of Nora Phillips.
Paul began to hum, and after a moment or two the humming broke out into a full-throated, but dubious baritone:
"Round and round and round go the deuterons
Round and round the magnet swings 'em
Round and round and round go the deuterons
SMACK! in the target go the microamps!"