File:TwentyFiveZones.png

English: Radar-separation hypersurfaces^[1] for an accelerated traveler, defined as the average proper-time of sending/receiving a light signal to/from an event i.e. τ_event = (τ_send+τ_receive)/2. Using the axis-labeled units, this is basically a one-gee (~1[ly/y²]) constant proper-acceleration round-trip which takes 4 traveler years to complete.

Four purple dots mark engine on/off events as well as the two mid-voyage points at which the direction of acceleration is reversed. Null trajectories extending forward and back from these points define twenty-five separate event-regions in space-time.

These zones (marked off by faint dotted lines) have blue radar-isochrons, and radar-distance grid-lines, drawn in to characterize for events from the accelerated traveler perspective. Separations in this case are at intervals of 0.2 (years or lightyears) from the traveler's radar-perspective.

The two vertical dashed lines (brown) represent the world lines of home and destination sites that are stationary in the x-ct coordinate system here. Following the separation between start and return isochrons into the flat-space region to the right will allow you to measure the triptime elapsed on the traveler's clocks using the ct-axis calibration here.