Tag Archives: sirius

Ptolemiac Universe Model

More Starlore: Astrology, not Planetology.

The fixed stars in astrology are perhaps the most forgotten part of the whole art.  It’s disappointing to think that they’ve been mostly forgotten, when it’s the stars themselves that are the very foundation of the astrological art.  There are several misconceptions about the fixed stars, ranging from their usage to their mechanics, hopefully we can correct some of these misconceptions.

Mechanics of the Stars

The fixed stars are hardly fixed.  They all move, and the astrologers of the Hellenistic, Classical, and Ancient times all knew the stars moved.  The fact of the matter being that the stars moved incredibly slowly.  This is not to be confused with the apparent motion of the stars in the sky which is daily motion, that’s something completely different.  Everything makes a rotation through the sky in a 24 hour period which is most usually seen in the rising and setting of the sun and moon.  However, the other planets and stars do the same thing, or at least they appear to, but for argument’s and simplicity’s sake, we’ll just say they do.  Thanks to procession, the stars appear to move through the sky in their own circle, independent of daily motion and the motion of the other planets.

In the Ptolemaic universe, the earth is thought to be at the center with the Ptolemiac Universe Modelplanetary orbs circling around it.  The orbs go in order from fastest to slowest planet effectively assigning the orbs in the order of Moon, Mercury, Venus, Sun, Mars, Jupiter, and Saturn.  After the orb of Saturn is thought to be the firmament, wherein rests the realm of the fixed stars.  The final orb in the universe is called the prime mover and is the orb that pushes all of the other orbs along in daily motion.  This is the only orb whose motion affects the lesser orbs and is the culprit of making the stars and planets appear to rise and set above and below our horizons.  The rest of the celestial spheres are thought to move on their own accord at their own speed.

Many skeptics of astrology will cite procession of the equinoxes as a reason for its dismissal and seem to automatically assume that the ancient and classical authors were oblivious to the phenomena.  However, the Ptolemaic universe itself is evidence enough that procession was known about and acknowledged during this time, the fact that the fixed stars have been allotted their own orb of motion shows that the knowledge of their motion (however slow that motion was) was common knowledge.  They just apparently didn’t care enough about procession to have it dismiss astrology since most were using a tropical zodiac anyway.

Calculating Stars in Charts

A horoscope is a two dimensional representation of a three dimensional sphere of space.  Now, obviously one dimension has been sacrificed for easy representation on paper, that dimension being depth.  While planets are located in the sky by zodiacal longitude represented by their position in the zodiac, they are also further located by their location north or south of the celestial equator, this is called declination.  Use of these two calculations is a useful way of locating planets and stars astrologically.  However, the idea that planets and stars are neatly lined up along the zodiac is just plain incorrect, they are also located above and below the zodiac.  Now, declination is not to be confused with inclination.  Inclination is the distance north or south of the ecliptic, which is the apparent path of the sun.  As you can tell, they have two different bases, one being the celestial equator (which is the earth’s equator projected onto the celestial sphere) and the other being the ecliptic.  Be careful not to get confused. Continue reading