# North node, South node correct understanding

What is the correct concept of the North node and South node? There is some conflicting information on the internet.

Which one of these two is correct?

1. Sourced from some Astrology material - How can North and South be 180-degree opposites in this since these are on one side of the orbit curve? https://www.spiritdaughter.com/blogs/align-with-magic/a-shift-in-perspective-the-north-node-moves-to-gemini http://astrologyclub.org/eclipses-and-the-moons-nodes/  2.From Wikipedia source - This seems incorrect too since there is no "separate" Moon orbit as per around the Sun

• Hi. Can you provide links to the original figures? There may be some description that clarifies them. Dec 23, 2020 at 3:57
• The first figure uses a lot of "artistic license". If we are to assume that the portion of the Moon's orbit that goes "over the top of the Earth" is the portion above the ecliptic plane, then the North and South nodes are labeled correctly. They should be 180 degrees apart because the intersection of 2 planes is a straight line. Dec 23, 2020 at 3:59
• The second figure has the symbols for ascending and descending nodes reverses, but is otherwise reasonable except that the two nodes are not 180 degrees apart. Dec 23, 2020 at 3:59
• @JohnHoltz Updated the question with links. If the first one is correct then the North node and the south node can not be exactly 180 opposite. If the second one is correct then the Moon doesn't have its own orbit around the Sun. Dec 23, 2020 at 5:29

The first few diagrams show the lunar nodes coinciding with the first and last quarter phases, which is only the case every 173 days or so. When the nodes are aligned with the new and full phases, eclipses can occur: In this diagram from timeanddate.com, our point of view is north of the ecliptic, the ascending node ☊ is in the 5 o'clock direction, and the descending node ☋ is in the 11 o'clock direction. Nodal precession moves them retrograde (clockwise from north) about 19.4° per year, an 18.6 year cycle mostly due to the Sun's gravity.

𝟏. In astronomy (as opposed to astrology, a pseudoscience which was often proven wrong), we don’t talk about “north” and “south” nodes, but about “ascending” and “descending” nodes.

𝟐. The first two images and the fourth one show the Earth’s orbit as too tight a curve; this is what makes you have a hard time understanding. Since they come from astrology-related sources, I’m not surprised they can’t be trusted.

𝟑. The ascending node is the place where the Moon crosses the apparent yearly path of the Sun (the “ecliptic”) from the south to the north; the descending node is where the Moon crosses the ecliptic from the north to the south. This is the only proper definition.

𝟒. As JohnHoltz correctly stated, the intersection of two planes is a line, so ascending and descending nodes are indeed at 180° from each other indeed, as the third, fifth, and sixth images show. (Actually, the difference is not exactly 180°, because gravitational perturbations make the orbit, an ellipse rather than a circle, slowly turn with respect to the fixed stars. Hence, the line of nodes makes a full 360° turn in about 18.61 years. By the time the Moon reaches the next node, it has thus advanced a little [by about 1.5°, from a quick calculation]).

• How did you calculate 18.61 years? Can you explain that? that is very interesting. Dec 23, 2020 at 5:56
• Well, I did not calculate it; it comes from Wikipedia and many other sources. en.wikipedia.org/wiki/Lunar_node (I’m sure there is a way to calculate it, but there’s no room for that in a comment.) Dec 24, 2020 at 1:26