Planetary station calendar
Find changes between direct and retrograde apparent geocentric longitude motion over a bounded date window.
Your inputs
Start with the example values, then replace them with your own. For tables, keep the vertical bar separators and use a dot for decimals.
This simplified educational calculation has stated assumptions. Do not use it for navigation, engineering safety or other safety-critical decisions.
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Result and workspace
Use the start button to open your result or activity.
How it works
Estimate longitude speed with a centered two-hour difference, find sign changes in six-hour samples, and refine each crossing to one second of numerical resolution. This is a geometric station estimate, not an astrological prediction; tangent zero-speed events without a sign change may be missed.
Worked example
These sample results use the original example inputs in the form. They do not change when you edit your inputs; your own result appears in the workspace.
- Station crossings: 4
| UTC instant | Longitude | Motion after station |
|---|---|---|
| 2026-10-24T07:15:19.665Z | 230.9796 | Retrograde motion begins |
| 2026-11-13T15:52:12.751Z | 215.0339 | Direct motion begins |
| 2027-02-09T17:35:42.883Z | 335.9826 | Retrograde motion begins |
| 2027-03-03T12:34:51.906Z | 320.924 | Direct motion begins |
Read the result carefully
Results depend on the values and assumptions shown above. Change one input at a time to see its effect. A blank or unavailable result means the data does not support a calculation; it is not zero.