The most memorable landscape photographs are often alignments: the sun setting exactly in the notch of a canyon, the full moon rising behind a lighthouse, the last light threading a city street. These are not luck. They are geometry, and the Planner is built to do the geometry for you.
Every celestial body has two coordinates at any moment: altitude (how high above the horizon) and azimuth (compass direction, 0° north through 90° east, 180° south, 270° west). Lightpath draws the azimuth of the sun, the moon and the Milky Way core as lines from your spot on the map. Where a line crosses your landmark, that is where the body will appear from where you stand.
Because the sun's setting azimuth swings roughly 60° between the June and December solstices at mid-latitudes, most alignments only happen a few days a year. The trick is finding those days.
If you save a recipe while the sun is near the horizon, Lightpath stores the alignment: which body, rise or set, and the azimuth to within about a degree. From then on the Return alert card on the Today tab computes the next date the same body will rise or set at that same azimuth from that spot, and schedules a local notification the evening before. This is how you turn one lucky sunset into an annual appointment.
The search runs up to 420 days ahead. Sun alignments recur roughly twice a year (once on the way to each solstice); moon alignments are messier because the moon's cycle is 18.6 years, so the app searches night by night.
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