| ultramarin marine translations |
| ultramarin.online | ||||
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draconitische maand | tijdspanne tussen twee opeenvolgende passages van de maan door de opstijgende knopen. Gemiddelde duur 27,2122 dagen, resp. 27d 5h 5min 36sec. Wegens de teruggang van de knopenlijn is de draconitische maand iets korter dan de siderische maand (27,3717d). |  |
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drakonitischer Monat Drachenmonat |
Zeitspanne zwischen zwei aufeinanderfolgenden Durchgängen des Mondes durch den aufsteigenden Knoten (dem Schnittpunkt der Umlaufebene des Monds und der Ebene der Ekliptik, s.u.). Dauer im Mittel 27,2122 Tage, bzw. 27d 5h 5min 36sec. Wegen der Rückläufigkeit der Knotenlinie ist der drakonitische Monat etwas kürzer als der siderische Monat (27,3217d). | ||
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nodal month dragon month draconi(ti)c month |
refers to the mythological dragon that lives in the nodes and regularly eats the Sun or Moon during an eclipse. The orbit of the Moon lies in a plane that is tilted with respect to the plane of the ecliptic: it has an inclination of about five degrees. The line of intersection of these planes defines two points on the celestial sphere: the ascending and descending nodes. The plane of the Moon's orbit precesses over a full circle in about 18,6 years, so the nodes move backwards over the ecliptic with the same period. Hence the time it takes the Moon to return to the same node is again shorter than a sidereal month.. The draconitic month lasts 27,212 220 days (27 d 5 h 5 min 36 s), or about 27 1/5 days. It is important for predicting eclipses: these take place when the Sun, Earth and Moon are on a line. Now (as seen from the earth) the Sun moves along the ecliptic, while the Moon moves along its own orbit that is inclined on the ecliptic. The three bodies are only on a line when the Moon is on the ecliptic, i. e. when it is at one of the nodes. At this time a solar or lunar eclipse is possible. | ||
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mois draconitique | l'intervalle de temps qui sépare deux passages de la Lune au noeud ascendant de son orbite (une des intersections de l'orbite lunaire et du plan de révolution de la Terre autour du Soleil). Il vaut 27.2122 jours. | ||
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