The ancient Babylonians found that 223 synodic months, 242 nodical months, and 239 anomalistic months all contained about 6,585 1/3 days, which turns out to be just 11 days in excess of 18 years.
The draconic month, the old and still better name for a nodical month, gets its name from the dragon that eats the sun when there's a eclipse - eclipses can only happen when the moon is at a node.
The nodical period is the period between two crossings of the ecliptic in the same direction.
Because 31 days is longer than the nodical month, there must be at least one solar eclipse of some description in each eclipse season, making two each year.
The duration of the nodical month is approximately 27.2122 mean solar days.
Definition of nodical in US English:
nodical
adjective
Astronomy
Relating to a node or the nodes of an orbit.
〔天文〕（轨道）交点的；与交点有关的
Example sentencesExamples
The draconic month, the old and still better name for a nodical month, gets its name from the dragon that eats the sun when there's a eclipse - eclipses can only happen when the moon is at a node.
Because 31 days is longer than the nodical month, there must be at least one solar eclipse of some description in each eclipse season, making two each year.
The ancient Babylonians found that 223 synodic months, 242 nodical months, and 239 anomalistic months all contained about 6,585 1/3 days, which turns out to be just 11 days in excess of 18 years.
The duration of the nodical month is approximately 27.2122 mean solar days.
The nodical period is the period between two crossings of the ecliptic in the same direction.