Per-location planning
Rank the atlas for your sky.
Choose a northern latitude, longitude, date, month, and sky darkness. The seasonal month view still ranks geometry and member-star visibility; the best-hour tonight view intersects asterism altitude, astronomical twilight, and the deterministic 2026 Moon heuristic. For offline field use, print the default 50°N tonight-planner card.
Pure-client planning model: schematic local clock from longitude, approximate astronomical twilight (Sun below −18°), no weather/terrain/time-zone database, and no minute-accurate ephemeris. Moon phase/rise/set is the deterministic 2026 heuristic from Cycle 5; outside 2026 the Moon flag is explicitly withheld.
Ranked observability
Tonight times are heuristic local clock times. The date drives the best-hour readout; the month selector remains for the seasonal/month-average ranking.
Visibility status is based on member-star V magnitudes versus the selected limiting magnitude. With Moon penalty enabled, the month-average moonlight loss is subtracted from that seasonal limit; the tonight column separately flags Moon interference at the best hour when the selected date is in 2026.
| Rank | Asterism | Best-month | Transit altitude | Hours above 20° | Best window tonight | Geometry | Sky visibility | Moon at best hour | Monthly Moon penalty |
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