Friday, May 15, 2009
Primary versus Zodiacal Motion: An Example
I recently had a question from a student that I wanted to post since I thought it touched on some useful astronomical/astrological concepts.
The question had to do with the upcoming election for the fixed star Alkaid, which is at 27 Virgo.
At the student's location the Moon on May 31, 2009 at at 17 Virgo and on June 1, 2009 at around 1 Libra. They knew that the Moon needed to apply to Alkaid and Alkaid had to be rising, ie on the Ascendant. They felt that because the Moon was rising in June 1 and would pass over the Ascendant as she rose that this was applying.
However, in fact, the May 31 election was the proper one! Why is this?
What we need to keep in mind is that there are two types of motion involved here, primary motion and Zodiacal motion.
The primary motion of the whole Heavens which causes the Sun and Moon to rise and the fixed stars to move, making a complete rotation in 24 hours. This is caused by the rotation of the Earth, from a heliocentric perspective and by the motion of the sphere of the fixed stars in the geocentric perspective. This makes the Moon move in a clockwise motion on the chart. Primary motion changes the location of planets, stars, etc., in terms of their house position because the house position is based on local space, that is looking from the position of the observer, wherever they may be located on Earth.
At the same time the Moon is orbiting the Earth and moving through the Zodiac, so while she has risen into the 12th house due to primary motion, she is also moving counterclockwise, in the order of the signs. Thus she is also moving from 17 Virgo where she is now towards 27 Virgo where Alkaid is. Zodiacal motion does not depend local space and is the same for all observers, no matter what their location. We do not measure aspects by primary motion, the motion produced by the Earth's rotation, but by the motion of the planets in their orbit, their motion through the Zodiac.
The Moon will not reach the Ascendant and perfect her conjunction with Alkaid with Alkaid on the Ascendant. But that is not necessary! The power of the conjunction is effective so long as she is within orb of an applying aspect. She aspects, literally beholds or sees the Ascendant and Alkaid, because she is within orb and therefore has an effect on them.
Again, think of the requirements of the election at one particular time or time range we have:
1. Alkaid rising, ie conjunct the Ascendant, so 27 Virgo is on the Ascendant.
2. The Moon is at 17 Virgo, applying to a conjunction of the Ascendant
We need not have the Moon at 27 Virgo and 27 Virgo rising! All we need is 27 Virgo rising and the Moon within her orb, say about 12 degrees. She could be at 15 Virgo and it would be usable.
More on Fixed Stars