One record per aspect. The origin says what kind of thing each value is; the source says where it came from; the limit says what it cannot tell you.
Eclipses, seasons, oppositions and elongations
The sky-events calendar (.ics) and the in-app event list are computed with astronomy-engine for a rolling 24-month window: global solar and lunar eclipse circumstances, equinoxes and solstices, planetary oppositions and greatest elongations.
EpochGeneration date plus 24 months
Methodscripts/generate-sky-events.mjs (SearchGlobalSolarEclipse, SearchLunarEclipse, Seasons, relative-longitude search for oppositions).
LimitGlobal circumstances only. Local eclipse contact times come from the per-city eclipse pages, which repeat the calculation for one observer.
Meteor shower maxima
Shower activity windows, radiants, ZHR and the solar longitude of maximum follow the IMO working list. The peak instant for a given year is found by searching for the Sun reaching that longitude, so it moves with the calendar rather than sitting on a fixed date.
MethodOne shared table (src/shared/meteorShowers.js) feeds the app, the emails and the .ics file.
LimitObserved rates vary from year to year; the ZHR is the nominal maximum.
Live alerts: asteroid close approaches
Close approaches inside the Moon's distance come from the JPL CNEOS close-approach API, with nominal and minimum distances and relative speed.
LimitNewly discovered objects can have large orbit uncertainty; the minimum distance is the 3-sigma bound.
Live alerts: bright novae and supernovae
The sky-alerts cron reads the "Bright Supernovae, Active Objects" list and keeps only transients brighter than magnitude 12 that were discovered within 30 days and observed within 14 days.
LimitAmateur-compiled registry; magnitudes are the latest reported estimates.
Live alerts: comet brightness
Observed comet magnitudes come from the COBS observation database (median of the most recent estimates over 45 days) and are compared with the catalog's predicted brightness law.
LimitVisual estimates by many observers; scatter of half a magnitude is normal.
Live alerts: geomagnetic storms
Geomagnetic watches, warnings and alerts are read from NOAA SWPC and stored with their issue time and G-scale level.
LimitA watch is a forecast, not an observation; the Kp value is the storm measure.
Space Time