AN APPARENT CHANGE OF DIRECTION
Find the two turning points.
A planet drifts east → west → east against the sky. Spend 12 observation nights to find when each reversal happens, then mark both dates within 4 days. An observation reveals its position and daily drift.
CAMPAIGN
Start near the middle. A westward reading lies between the two turns.
Observation notebook
Science, controls & source
Measurements come from Astronomy Engine by Don Cross (MIT), using light-time and aberration corrected geocentric positions converted to true ecliptic coordinates of date. Daily drift is a centered one-day difference. Turns are found on a one-day grid, so this is an educational investigation, not a precision observing planner. Position angles are unwrapped across 360° for plotting. Straight dotted segments connect only measured points; they are not predictions.
Use sliders with touch or arrow keys. The day buttons step the observation date. Reset restores the same case; new window changes the date range around the same historical event. Four planets have different drift speeds and reversal intervals. GPT-generated planet plates are integrated into campaign selection. Source: cosinekitty/astronomy at 865d3da. License.