Science / Tides and Currents / Declination: Angular distance north or south of the celestial equator, taken as positive when north of the equator and negative when south. The Sun passes through its declinational cycle once a year, reaching its maximum north declination of approximately 23-??° about June 21 and its maximum south declination of approximately 23-??° about December 21. The Moon has an average declinational cycle of 27-?? days which is called a tropical month. Tides or tidal currents occurring near the times of maximum north or south declination of the Moon are called tropic tides or tropic currents, and those occurring when the Moon is over the Equator are called equatorial tides or equatorial currents. The maximum declination reached by the Moon in successive months depends upon the longitude of the Moon's node, and varies from 28-??° when the longitude of the ascending node is 0°, to 18-??° when the longitude of the node is 180° . The node cycle, or time required for the node to complete a circuit of 360° of longitude, is approximately 18.6 years. See epoch (2).

Declinational Reduction

Science / Tides and Currents / Declinational Reduction: A processing of observed high and low waters or flood and ebb tidal currents to obtain quantities depending upon changes in the declination of the Moon; such as tropic ranges or speeds, height or spee MORE

Magnetic Declination

Science / Geology / Magnetic Declination: The horizontal angular difference between True North and Magnetic North. MORE

Tropic Tides

Science / Tides and Currents / Tropic Tides: Tides occurring semi-monthly when the effect of the Moon's maximum declination is greatest. At these times there is a tendency for an increase in the diurnal range. The tidal datums pertaining to the MORE