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A lunar node is either of the two orbital nodes of the Moon, that is, the two points at which the orbit of the Moon intersects the ecliptic. The ascending (or north) node is where the Moon moves into the northern ecliptic hemisphere, while the descending (or south) node is where the Moon enters the southern ecliptic hemisphere. A lunar eclipse can occur only when the full Moon is near either lunar node (within 11° 38' ecliptic longitude), while a solar eclipse can occur only when the new Moon is near either lunar node (within 17° 25'). Both solar eclipses of July 2000 (on the 1st and 31st days) occurred around the time when the Moon was at its ascending node. Ascending-node eclipses recur after one draconic year on average, which is about 0.94901 Gregorian year, as do descending-node eclipses. Because the orbital plane of the Moon precesses in space, the lunar nodes also precess around the ecliptic, completing one revolution (called a draconic or nodal period) in . (This is not the same length as a saros.) The same cycle measured against an inertial frame of reference, such as International Celestial Reference System (ICRS), a coordinate system relative to the fixed stars, is 18.599525 years. The nodes are called by different names in different cultures of the world. In medieval texts, the nodes are referred to as ras wa dhanav al-tinnîn in Arabic. rosh ha-teli u-zenavo (ראש התלי וזנבו) in Hebrew, and caput draconis (head of the dragon) or cauda draconis (tail of the dragon) in Latin. The ascending node is referred to as the dragon's head with the astronomical or astrological symbol of ☊ and the descending node is known as the dragon's tail with the symbol ☋. In Hindu astronomy, the nodes are considered with the seven planets among the nine Navagrahas; the ascending node ☊ is called Rahu and the descending node ☋ is called Ketu. In Tibetan astrology (partially based on the Kalachakra Tantra) these nodes are respectively named Rahu and Kalagni. Lunar standstill The Moon's orbit is inclined about 5.
Yves Perriard, Miroslav Markovic, Omar Scaglione