Ephemeris Graph
The ephemeris graph is the plotting surface that fills the right-hand side of the three graphic ephemeris study editors. It shows the shape of the data, where curves rise, fall, cross, or turn, which a table of numbers cannot convey at a glance.
The graph draws one curve per selected body and metric against a horizontal time axis, with a separate value axis for each plotted metric and a legend identifying the series. Each body's curve is drawn in the color assigned to it in Graph Settings. When the plot first appears, the visible time window opens on the most recent part of the generated span.
Show or Hide a Plotted Metric
To add a measurement to the plot, or take one off it:
- Click the checkbox beside the metric's name in the Metrics list.
The plot redraws without generating the study again, because the generated series already carry all four plottable metrics. Only Longitude, Latitude, Distance, and Speed are offered on a graphic study; Sign Position has no graphic counterpart. See Body Metrics List.
The Bodies list is locked by the completed generation, so changing which bodies are plotted means unlocking the study and generating it again. Changing which metrics are plotted does not.
Gestures on the Plot
Once the study has been generated, the plot responds to the pointer gestures below, each documented on its own page:
- Read a value off a curve: rest the pointer near a curve for a crosshair and a three-line readout. See Graph Series Hover Readout.
- Adjust a value axis: drag on an axis to magnify or compress the metric it scales. See Adjust a Graph Value Axis Range.
- Pan the time window: drag inside the plot to move backward or forward through the generated span. See Pan the Graph Time Window.
- Zoom the time window: drag on the time axis strip at the foot of the plot to widen or narrow the visible period. See Zoom the Graph Time Window.
Value-axis adjustments are kept with the study and restored the next time you open it. The time window is not: it is deliberately recomputed each time the study is opened, so panning and zooming never leave you somewhere unexpected later.
Units
Distance values are plotted in AU and speed values in degrees per day, the same units the ephemeris table reports.