The Ecliptic System
The basis of this system is formed by the plane of the Ecliptic. In this plane, starting from the centre of the Earth, the North-South axis of the Ecliptics is erected. This axis in turn provides the suspension points for the great circles from which the latitude co-ordinates can be read.
fig 5.2.c. the Ecliptic System
From the same observation point, we will view the Ecliptic System from an ever-changing angle, according to the progress of the seasons.
The co-ordinates of this system are called longitude and latitude degrees.
This is the system used in the Ephemeris and the Nautical Almanac, to indicate the positions of the planets.