Star Almanack · Calculation tools

Ephemera

Positions and rise/set times at a date, time and observing location.

Ephemeris generator

Choose a city or enter coordinates, then choose an instant. Your device calculates the positions and rise/set times here, using astronomy data stored with this site.

Choose a match to fill coordinates, estimated elevation and timezone. Smaller places can be entered by coordinates.

Choose a date and time in the selected time zone. Current date range: 1900–2099; dates at the source-data boundaries may be unavailable.

Rise/set cover the local calendar date containing this instant in the selected timezone. Daylight-saving changes are included. Coordinate edits do not change the timezone; check it when moving to a different location.

Ready. The first calculation downloads the engine and astronomy data (about 60 MB). No account or Python installation is needed.

What the report contains

Sun, Moon, Mercury, Venus, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune and Pluto. Earth is the observer's origin, not an output row. The HTML and JSON reports include right ascension, declination, ecliptic coordinates, altitude, azimuth, and rise/set events.

Method and limitations

Positions are recalculated as time advances; rise/set times are not estimated from the weekly 9 PM snapshot. Coordinates use topocentric apparent positions; RA/Dec use ICRF axes. Values are provisional pending validation. The model uses standard atmospheric refraction and the Sun’s and Moon’s apparent radii, without local terrain, horizon dip or weather corrections, and the time scan may miss grazing events.

Calculations run on your device. City search and astronomy files come from this site; your chosen coordinates are not sent to a calculation service. The browser may cache downloaded files for later visits.

City locations adapted from GeoNames, CC BY 4.0. City elevation is an estimate. Calculation software and data credits.