Knowra Draconic month Draconic month The interval between successive passages of the Moon through the same orbital node, averaging about 27.21 days. It is shorter than a sidereal month because the lunar nodes move westward along the ecliptic.
Lunar node : A point where the Moon’s orbit crosses the ecliptic, Earth’s orbital plane. A draconic month runs from one crossing of the same node to the next.
Eclipse season : A period, occurring about every six months, when the Sun is near a lunar node and eclipses can occur. The Moon’s return to a node helps set the interval between eclipse seasons.
Synodic month : The average interval between successive identical lunar phases, about 29.53 days. It tracks Sun–Moon alignment, not the Moon’s return to an orbital node.
Inclination : The angle between an orbit’s plane and a chosen reference plane. The Moon’s orbital inclination makes its path cross the ecliptic at two nodes.
Nodal precession : The westward rotation of the Moon’s orbital plane, completing a cycle in about 18.6 years. As the nodes move westward, the Moon reaches them sooner than it completes a sidereal orbit.
Solar eclipse : An event in which the Moon passes between Earth and the Sun, obscuring some or all of the Sun. A solar eclipse requires the new Moon to occur near a node.
Anomalistic month : The average interval between successive lunar perigees, about 27.55 days. It measures return to closest approach to Earth rather than return to a node.
Orbital period : The time an object takes to complete one orbit around another object. A draconic month is an orbital period measured relative to a node.
Sidereal month : The Moon’s orbital period measured against the distant stars, about 27.32 days. Its longer duration shows the effect of moving nodes on the draconic month.
Lunar eclipse : An event in which the Moon passes through Earth’s shadow at full Moon. A lunar eclipse requires the full Moon to occur near a node.
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