Tonight gives a verdict, the best setup time and target, and a ledger of why: darkness, the worst forecast values in the window, the moon and how fresh the forecast is.
7 nights picks one target and window per night for the week ahead and adds up usable hours per target, which helps when building integration time on one object over several nights. Session is a six-hour workspace with a timeline, a sky chart, target comparison and framing against the DWARF 3’s telephoto field. Weather breaks the Open-Meteo forecast into cloud layers, wind and dew point.
All the astronomy runs in the browser. The only network request is the forecast, and there are no accounts, database or analytics. A window needs an hour of astronomical darkness with the target above 30°, and missing forecast data counts as unknown, never as clear.
The star catalog is hand-entered J2000 with no precession correction, so the sky chart is for orientation, not pointing.