I think you've almost got it.
sidus_illuminans wrote: Fri Jun 21, 2024 4:02 pm
Ah, it seems I was conflating two different data points. I failed to understand that Prime Vertical Longitude was different and had to be calculated separate from the chart.
Yes, this is not evident just by looking at a typical chart. What you see in a horoscope view in basically any software is called
longitude, or
ecliptical longitude when needed for clarity, which involves the signs of the zodiac; for example, going by Jim's figures, Saturn is at 17°09' Aquarius in your chart. This is its (ecliptical) longitude. (In most software, this is just called "longitude.")
Prime vertical longitude is a completely separate measurement that is not usually displayed in the horoscope view - although in Time Matters, a planet's distance into a sidereal house (which is measured in PVL) is displayed, which should make it clear at a glance if a planet is near Ascendant, Descendant, MC, or IC in PVL. It also shows the full ( 0-360°) PVL in the data table at the bottom, like you mention, which is another place to see that same information. There are other things which are called "longitude" too, like your
geographic longitude (i.e. of a place on earth, not a planet), or the relatively new calculation
Meridian Longitude. But for a planet, just referring to it's "longitude" always means "ecliptical longitude."
However, Zenith and Nadir are not measured in PVL. They are measured in
longitude, i.e. ecliptical longitude. They are exact squares to both Ascendant and Descendant.
Elsewhere you mentioned that the Nadir and Zenith contacts are ecliptical squares to Ascendant, but I am having difficulty understanding what this means. The Nadir and Zenith aren't at predefined angles the same way the Asc is always at 0°, right? In beginner friendly language, how might I calculate or determine these minor angles so that I can, for example, refine a given planet's placement in an SSR?
The Ascendant is always at 0° in PVL, but not
longitude. The Ascendant has a regular (ecliptical) longitude just like the other bodies on the chart, and conjunctions to Zenith and Nadir are measured purely in longitude.
You will typically not see points given on the chart for Zenith and Nadir, or the squares to MC, which are Eastpoint and Westpoint (and they work the same way in this context). You need to look at the longitude of the Ascendant, or MC, and go 3 signs over. For example, one charting software I have access to at the moment (Astro Vizor) gives the longitude of my Ascendant at 16°06' Leo. The signs that are square to Leo are Scorpio and Taurus. Therefore, the Nadir in my chart is at exactly 16°06'
Scorpio and the Zenith is at exactly 16°06'
Taurus. Taking a look just visually, Scorpio is at the exact bottom of the chart and Taurus is at the exact top, so that checks out.
However you get the longitude of the Asc and MC and the planets - a data table or a chart view - you can calculate it like this. I find it easiest to look at a chart view. In the next release of Time Matters (on the horizon, but not dropping immediately), information on these angles will appear in the data table at the bottom alongside the planets. That should help with these kinds of measurements.
I've been trying to wrap my head around finding the angle of the Nadir and thought looking at the planet's location on the chart relative to the angles might be a clue. I can see the PVL for a planet on a minor angle within Time Matters, but don't know the exact ° of the angle itself.
PVL is only used for conjunctions to major angles - Ascendant, MC, Descendant, and IC. It is not used for minor angles. For Eastpoint/Zenith/Westpoint/Nadir, only longitude is used. (There is another way of calculating conjunction to Eastpoint or Westpoint in
right ascension, which is another way of calculating a conjunction with one of those minor angles. These are given usually as EP-a, or alpha, and WP-a. Time Matters says that a planet on one of those angles is on Ea or Wa, respectively, due to character limits. I can go into that if you want but I don't want to throw even more info at you unless you want it.)
Does this answer your question?