In order to obtain the vertical position of a celestial (as opposed to its horizontal position along the ecliptic) we measure the distance of a planet north or south of the celestial equator—from which they are said to decline (either northward or southward). Every part of the ecliptic has declination, except the beginnings of Aries and Libra (0°00'), because the plane of the ecliptic is not parallel with that of the celestial equator and those two points are where the two planes intersect. The Sun has maximum declination of 23°28', when it reaches either the Tropic of Cancer in the north (23°N28'), or the Tropic of Capricorn in the south (23°S28'). Declination is due to the inclination of the earth in orbit. The Parallel and Contra-Parallel aspects are aspects of declination.