In the ecliptic coordinate system, the reference is the plane of the ecliptic—that is, the plane formed by Earth’s orbit around the sun. The orbits of the other planets in the solar system, with the except of Pluto, lie within 7° of this plane. (Pluto’s orbit is inclined 17° to the ecliptic.) The coordinates of an object are given as celestial longitude, measured eastward along the ecliptic from the vernal equinox, and celestial latitude, measured north (+) or south (-) from the ecliptic. This system is handy for studying the solar system.
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