Declination

Right Ascension (blue) and declination (green)

Astronomy

The measurement of angular distances to the North or South of the celestial equator which is an extension of the Earth's equator projected out into space. The declination is measured in degrees, minutes and seconds of arc. A planet is said to have a positive declination when it is located north of the celestial equator and negative declination when located South of it. The value always lies between 0 and 90 degrees, with 0 degrees being a location on the celestial equator, +90 degrees at the North Celestial Pole and –90 degrees at the South Celestial Pole. A planet's exact location can be given when the values of the declination and right ascension are taken together.

If one compares the coordinate system of the celestial sphere with that of the Earth – the former being a projected extension of the latter into outer space – the declination is equivalent to position of latitude on the Earth's surface.

The declination is not to be confused with the ecliptic latitude which measures the vertical angle of a planet to the equator.

Moon

When full, the Moon is opposite to the Sun not only in zodiacal longitude but also in declination. This means that when the Sun rises and sets at its northernmost and achieves its greatest altitude near the summer Solstice, the full Moon rises far south and rides low in the sky. In the winter, when the Sun rises and sets far south, the full Moon is high in the sky, as well as rising and setting at its northernmost point.

The Moon's orbit is tilted 5.2 degrees to the orbit of the earth (or Sun). Other perturbations can account for an additional .7 degrees variation, so the Moon's declination can differ from the Sun's by almost 6 degrees. This means that the Moon can achieve more than 29 degrees of declination (23.5 + 6), far more than any other planet.

See also

• Coordinate System
• Ecliptic
• Latitude
• Out-of-Bounds Planets
• Parallel

Weblinks

• Wikipedia: Declination
• Sun Motions Demonstrator (Flash-Animation)
• Declinations Ephemeris 1930-2024 PDF (without moon; cafeastrology.com)
• What is Declination? (Video David Cochrane, 2014)
• Selection of Ephemerides for 6000 years at Astrodienst (includes option for declinations and latitudes)
• Moon Teachings for the masses at the umass sunwheel & around the world: the major lunar standstlls of 2006 & 2024-25 (Dept. of Astronomy Univ. of Mass., Amherst)
• Moon Swings - The Lunar Standstill Cycle (Linea Van Horn, 2017; Astrodienst)

Bibliography

• Paul F. Newman: Declination in Astrology - The Steps of the Sun. Wessex Astrologer, Revised edition, 2006. ISBN 10: 1902405188, 212 pages. Review online (Sarah Fuhro, Skyscript 2010)