"Sun/Moon Midpoint
The third axis is the Sun/Moon midpoint. The concept of midpoints (see Halfway to Heaven) in astrology is a fairly new concept. Fact is, though, in mythology and alchemy - the Sun/Moon "midpoint" axis is quite old. Don't believe me?
From the alchemical writing "Theatrum Chemicum" (1613 AD)
Volume IV, XV Duodecim tractatus de lapide philosophorum, Anonymous
An excerpt as quoted by Carl Jung in his book Aion:
"the aqua rosis nostri (water of our dew), whose "mother is the midpoint of the heavenly and earthly Sun and Moon."
But so what in the heck does this mean?
In this tractatus (treatise) the anonymous alchemist has been discussing the properties of the "philosopher's stone." The philosopher's stone is the mysterious "magnet which draws all things to itself." (Keep in mind that in 1613 AD, we were still somewhat in awe of the "mysterious, magical" properties of magnets...)
The philosopher's stone was the initial substance that the alchemist was attempting to create through experimentation. With the philospher's stone, one could then transform the base metal of lead into valuable gold.
The author has further (in this passage) now equated the much sought after "philosopher's stone" with the "aqua rosis nostri" (water of our dew).
In Western alchemical writings, the royal marriage of the Sun (heavenly) and Moon (earthly) was the final transformation stage whereby the end product (i.e. gold) could be created. Out of the Sun/Moon conjunctio (the philosopher's stone), the alchemist's work of transforming base metals into gold can be finally be completed. The coming together of the Sun (heavenly) and Moon (earthly) is the mother which gives birth to the philosopher's stone.
If you managed to get lost in this boring explanation (and I can't blame you) - then here's the point:
The marriage (conjunctio) of the Sun and Moon - the coming together of heaven and earth - results in the philosopher's stone that in turn gives one the ability to transform spiritual lead and give birth to spiritual gold. Spiritual gold can potentially be created in our lives by the alchemical "coming together" of the combined energies (midpoint) of the Sun and the Moon.
To be sure, there are many, much older alchemy (ancient Greek) text referrals to the royal marriage of the Sun and Moon which I could have quoted here.... but this passage caught my fancy due to its usage of the word "midpoint." Obviously, the anonymous author is not referring to our modern zodiacal calculations of the Sun/Moon midpoint axis. Or then again maybe he/she is…
And of the three axes I've mentioned in this section - the Sun/Moon midpoint axis is the one which interests me the most. I sometimes wonder if a big part of my fascination is that nobody really "messes" with it much... no one seems to be particularly interested...
However, I shouldn't make a blanket statement that absolutely no one is interested in the Sun/Moon midpoint...
In the fascinating writings of Helen Adams Garrett, The Karmic Horoscope, she utilized the Sun/Moon midpoint in a big way! She used it as what she called the "Karmic Degree" and with it formed a totally new chart, placing the Sun/Moon midpoint where the Ascendant degree normally goes. It's part and parcel of a very fascinating (speculative) theory that I won't go into here. If interested, you should fork out some bucks and buy the book."
https://thezodiac.com/sun.htm