Ephemeris Settings

The Ephemeris Settings anchor every calculation a study performs. They combine a Location, which drives the time zone used for all dates and times, with the Reference System, which defines the coordinate framework the positions are measured in.

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A location is required before you can generate events. Every event's date and time is computed in the selected location's time zone.

Location

The Location dropdown lists the places you have saved in your Locations library. Each location carries a name, its coordinates, and its time zone. Because the list reflects whatever you have saved, it changes as you add, edit, and remove locations in the Locations Editor.

Selecting a location sets the time zone used for every event's date and time.

Reference System

The Reference System is made up of three settings that determine how celestial positions are measured: the Zodiac, the Coordinate Origin, and the Reference Plane.

Zodiac

Option	Description
Tropical	Longitudes measured from the vernal equinox.
Sidereal	Longitudes measured relative to the fixed stars.

Coordinate Origin

Option	Description
Geocentric	Positions measured from the center of the Earth.
Topocentric	Positions measured from the study's location on the Earth's surface.
Heliocentric	Positions measured from the center of the Sun.

Some studies offer only Geocentric and Topocentric; on those studies the Heliocentric option does not appear.

Reference Plane

Option	Description
Ecliptic	Positions expressed as ecliptic longitude and latitude, relative to the plane of the Earth's orbit.
Equatorial	Positions expressed as right ascension and declination, relative to the celestial equator.

Configuring the Ephemeris Settings

To anchor a study's calculation:

• Choose a Location, then set the Reference System (Zodiac, Coordinate Origin, Reference Plane) to the framework you want to work in.

To save a Location and Reference System combination for reuse across studies, see Ephemeris Presets.