Aspects of this topic are discussed in the following places at Britannica.
...27.321582 days (i.e., 27 days 7 hours 43 minutes 5 seconds), only 7 seconds shorter than the sidereal month, is the time between passages of the Moon through the same celestial longitude. The draconic, or nodical, month of 27.212220 days (i.e., 27 days 5 hours 5 minutes 35.8 seconds) is the time between the Moon’s passages through the same node, or intersection of its orbit with...
...north to south. The nodes move along the ecliptic from east to west as seen from Earth, completing a revolution in 18.6 years. The Moon’s revolution from one node to the same node again (called the draconic month, 27.212220 days) takes somewhat less time than a revolution from new moon to new moon (the synodic month, 29.530589 days). For a solar or lunar eclipse to occur, the Moon has to be...
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