Editing Lunar node (section)

==Eclipses==
[[File:Eclipse vs new or full moons, annotated.svg|thumb|left|[[Nodal precession]] of the lunar nodes as the Earth revolves around the Sun causes an [[eclipse season]] approximately every six months]]

A [[lunar eclipse]] can occur only when the [[full moon|full Moon]] is near either lunar node (within 11° 38' ecliptic longitude), while a [[solar eclipse]] can occur only when the [[new moon|new Moon]] is near either lunar node (within 17° 25').

Both solar eclipses of July 2000 (on the [[solar eclipse of July 1, 2000|1st]] and [[solar eclipse of July 31, 2000|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.

An [[Eclipse]] of the Moon or Sun can occur when the nodes align with the Sun, roughly every 173.3 days. Lunar orbit inclination also determines eclipses; shadows cross when nodes coincide with full and new moon when the Sun, Earth, and Moon align in three dimensions.

In effect, this means that the "[[tropical year]]" on the Moon is only 347 days long. This is called the ''[[draconic year]]'' (or ''eclipse year''). The "seasons" on the Moon fit into this period. For about half of this draconic year, the Sun is north of the lunar equator (but at most 1.543°), and for the other half, it is south of the lunar equator. Obviously, the effect of these seasons is minor compared to the difference between lunar night and lunar day. At the lunar poles, instead of usual lunar days and nights of about 15 Earth days, the Sun will be "up" for 173 days as it will be "down"; polar sunrise and sunset takes 18 days each year. "Up" here means that the centre of the Sun is above the horizon. Lunar polar sunrises and sunsets occur around the time of eclipses (solar or lunar). For example, at the [[Solar eclipse of March 9, 2016]], the Moon was near its descending node, and the Sun was near the point in the sky where the equator of the Moon crosses the ecliptic. When the Sun reaches that point, the center of the Sun sets at the lunar north pole and rises at the lunar south pole.