Lunar moon change

[arumdyaharum]

In astrology we have north node and south node that change the longitude almost every day. I tried code like this

function moonNode (date) {
  console.log(date);
  const node = Astronomy.SearchMoonNode(date);
  const eclip = Astronomy.EclipticGeoMoon(node.time);
  const type = node.kind = 1 ? "North node" : "South node"
  const degree = Math.floor(eclip.lon);
  const minutes = Math.floor((eclip.lon - degree) * 60) 
  console.log(type + ' ' + degree + ' ' + minutes)
  return eclip.lon;
}

the output was this

1998-04-03T00:00:00.000Z
North node 160 8
1998-01-05T14:13:56.903Z
North node 161 15

but after I check on the astrology empheris (https://www.astro.com/tmpd/c8yhfileyS5iO5-u1687025000/astro_d5eph_d.65025.59325.pdf), the actual degree (with adding 150 because it's in virgo) is this

1998-04-03
North Node 160 4
South Node 158 51

1998-01-05
North Node 162 16
South Node 163 31

How can I get the correct lunar node longitude like astrology empheris?

[cosinekitty]

The ephemeris you referenced from astro.com appears to be showing the Moon's ecliptic longitude at exactly 00:00 UTC. However, in the Javascript code you posted, you are searching for the next time the Moon crosses through the ecliptic plane, which is not the same time. In fact, it can be as many as 15 days later. Can you try adding this line of code?

console.log(`Node at ${node.time}`);

This will show the time for which you are finding the Moon's ecliptic longitude.

I think what you meant to do is:

const eclip = Astronomy.EclipticGeoMoon(date);

[cosinekitty]

OK, this is good, because now I know we are talking about the same thing. The "north node" is the same thing I call an ascending node in Astronomy Engine, and the "south node" is the same thing I call the descending node. However, the first remark you made in this discussion still confuses me:

In astrology we have north node and south node that change the longitude almost every day.

I don't know what you mean when you say the nodes change longitude almost every day. There are only 2 nodes, ascending and descending, and each happens only once during a given lunar orbit. So on average, there is one ascending node every 29 days and one descending node every 29 days. Neither of these can happen every day. Each occurs at a very specific time and longitude. Both happen at a fixed point at a fixed time, not changing every day. However, like the above quoted reference mentions, the longitude is different for each lunar month.

So I still feel like there is a problem where I don't understand what you are trying to do, or how Astronomy Engine's functionality is lacking for that case.

[arumdyaharum]

I tried to use two eclipse date around the date I enter and then I create percentage from those two date so I can get the longitude of the date I enter. I get pretty close degree to what I expected. here's my code

function lunarNodes (date) {
  const node = Astronomy.SearchMoonNode(date);
  let c = new Date(date);
  let flag = true;
  let nodeBefore = node;
  while(flag) {
    c.setDate(c.getDate() - 5);
    nodeBefore = Astronomy.SearchMoonNode(c);
    if (nodeBefore.time.date.getDate() !== node.time.date.getDate()) flag = false;
  }
  const eclip = Astronomy.EclipticGeoMoon(node.time);
  const eclipBefore = Astronomy.EclipticGeoMoon(nodeBefore.time);
  const q = Math.abs(date - nodeBefore.time.date);
  const d = Math.abs(node.time.date - nodeBefore.time.date);
  const fraction = (q/d);
  const currentElon = (eclip.lon - eclipBefore.lon) * (fraction / 100);
  return nodeBefore.kind > node.kind ? eclip.lon + 180 - currentElon : eclip.lon - currentElon;
}

[JoyL8896]

interesting

[venu-mallik]

@arumdyaharum I am not sure if the accuracy is enough for you, formulae is in page 65.
Formula : https://literature.hpcalc.org/community/astronomical-formulae.pdf

[arumdyaharum]

@vrworkers thank you for the reference. I don't have any astronomical background so it's quite confusing. though I find it helpful to learn about astronomy.

[arumdyaharum]

Hi again. I wanna update this discussion. I shared my human design program https://github.com/arumdyaharum/hdkit if you wanna know how I use this. if you run the program, you'll get gate, line, color, tone, and base. basically what it does is dividing gates into lines, lines into colors, etc. so the accuracy of the degree or longitude is crucial.

tbh I'm confused when I wrote this answer of mine. so I refactor it like this.

function lunarNode (date) {
  const node = Astronomy.SearchMoonNode(date);
  const eclip = Astronomy.EclipticGeoMoon(node.time);
  const eclipLon = node.kind < 0 ? (eclip.lon + 180) % 360 : eclip.lon
  if (node.time.date === date) return eclipLon;
  let tempDate = new Date(date);
  let flag = true;
  let nodeBefore = node;
  while(flag) {
    tempDate.setDate(tempDate.getDate() - 10);
    nodeBefore = Astronomy.SearchMoonNode(tempDate);
    if (nodeBefore.time.date.getDate() !== node.time.date.getDate()) flag = false;
  }
  const eclipBefore = Astronomy.EclipticGeoMoon(nodeBefore.time);
  const eclipBeforeLon = nodeBefore.kind < 0 ? (eclipBefore.lon + 180) % 360 : eclipBefore.lon
  const d = Math.abs(node.time.date - nodeBefore.time.date);
  const a = Math.abs(node.time.date - date);
  const fraction = (a/d);
  let angle = eclipBeforeLon - eclipLon;
  angle = angle * fraction;
  const currentEclip = eclipLon + angle;
  // version 2 : with the constant of lunar nodes regression's rate 
  // const time = a / (365.25 * 24 * 60 * 60 * 1000);
  // const angle = 19.32 * time;
  // const currentEclip = eclipLon + angle;
  return currentEclip;
}

it's getting the lunar node's gates and line right, but if I wanna get the color and tone, the accuracy is not consistent especially before 2000. I know it's accurate or not by comparing my data to www.humdes.com data. lunar node's color and tone is used for creating the direction of bottom arrow. it also applies to the top arrow with sun's color and tone which if you see it's already accurate.