

The angular relationship between these two bodies defines the lunation cycle. The two most important parts of that cycle have been considered the New Moon (Sun-Moon conjunction) and Full Moon (Sun-Moon opposition). If either of these points occurs conjunct the nodal axis, then that lunation is also an eclipse. When one of these bodies is eclipsed, a shadow passes across the Earth in the region of visibility. A solar eclipse is only visible during the day, while a lunar eclipse is visible only at night. One of the high points of Hellenic astronomy was the discovery of the Metonic Cycle (although this discovery was not unique to the Greeks), which recognized a nineteen year cycle to eclipse patterns.

Astrologically, the typical meaning of the event is that something is eclipsed: a shadow passes over it; it become invisible. Usually, this is not considered a good thing.

The Sun and the Moon were the first chronocators in most societies: time keepers. The lunar calendar, which begins with the New Moon of every one of the 12-13 months per solar year, is still in use in Arabic and Jewish societies and households. In these calendars, the difference between the number of days in solar years and in the lunar months results in a seasonal shift of the months after a short period: this is corrected in soli-lunar calendars, which adjust the lunar calendar to the solar one by adding intercalary days.


Because the Moon moves so rapidly and has visible phases, it is easily possible to observe nightly changes in the Moon: the time of its rise, its shape, and its proximity to the Sun. Venus too has phases to the careful observer. But planetary movements are much slower - though observable. Once a coordinate system was mapped out against which observation could occur, the planetary cycles could first be observed, then understood (at least historically), and finally predicted based on past motion.

Planets could then be studied, not merely in isolation, but in respect to each other. This is where the aspects come in. The aspects are particular angular separations between planetary pairs that have been deemed to have particular significance. To understand the meaning of particular, we will digress briefly into harmonics. This is not really a digression, because this is one way that the aspects themselves were historically understood.

In the study of harmony, it was discovered that pleasing or dissonant tones could be produced by plucking or bowing strings of different lengths - where the ratio of the lengths of the strings would predict whether it would sound good or bad. This ratio idea was carried over into astrology: and it is likely that the earliest representations of these orbs were as ratios, not as degree numbers as we express them today.

The perfect or partile aspects are simply one degree, but normally an orb is allowed. "Partile" means in the degree. Let me illustrate with the conjunction: Venus and Mars are partile conjunct if they are at 1 Taurus 01 and 1 Taurus 59 respectively. But if one is at 1 Taurus 59 and the other is at 2 Taurus 01, they are not partile, although they are considered conjunct. The reason that this later orb - though closer - is platic (i.e., inexact), is that, following pythagorean arithmetic protocol, no rounding occurs: the minutes are truncated, not rounded, and only the degree number itself is used. (Numbers were considered too sacred to arbitrarily change.)

If we look at the so-called ptolemaic aspects below, I have expressed the aspect using both the modern degree convention, and the more ancient harmonic ratio.

Angular Separation
Relation to other Aspects
all other angles are divisible by this
1/2 the trine; 1/3 the opposition
1 1/2 a sextile = sesqui-sextile; half the opposition
twice the sextile
1 1/2 a trine = sesqui-trine; twice the square

Back to the issue of orbs. Orbs, or the amount of area surrounding the partile aspect that will still be allowed to be "within orb," have been of varying sizes. In Hellenistic astrology, the sign has such overriding importance that the "orb" was actually the entire sign. Thus, Venus at 29 Taurus is conjunct Mercury at 1 Taurus, but not conjunct Mars at 1 Gemini.

Occasional modern astrologers have also advocated whole sign orbs: one was Betty Lundsted, a rather typical East Coast astrologer who had a very busy practice in the 1970's and 1980's. Another modern example is Karen Hamaker-Zondag, who does not routinely use whole-sign orbs, but uses the break in sign to determine whether a planet is unaspected. Thus, she would agree that Venus is not conjunct Mars above, but she was also say that Venus isn't conjunct Mercury either.

The typical approach in the Middle Ages was to assign the orb size to each planet. Then, to determine whether two planets were in aspect, you would take half the orb size of each planet (this half is called the moiety) and add them together. Page 204 of Burk gives you the orb sizes used by William Lilly. You will also see an example of how to calculate an orb based on this system.

As Burk points out, it was Alan Leo who really started the ball rolling for assigning an orb to each type of aspect. Sometimes, a further elaboration was to assign a larger number to the Lights: you will observe in Lilly's table how much greater orb they traditionally had. The logical extension of this system was achieved by John Addey, a British astrologer known for his study of harmonics. Addey pointed out that, since the aspects themselves can be expressed as harmonics (thus, a square, is 1/4 of the circle; hence the 4th harmonic; a sextile is 1/6 of the circle, hence the 6th harmonic), then the orbs should be adjusted to compensate for the harmonic of the aspect itself.

For example, if you allow 12 degrees for the conjunction, then you allow 6 degrees for the opposition (remember, its ratio is half the conjunction), 4 degrees for the trine, 3 degrees for the square, and 2 degrees for the sextile. (These ratios are taken from David Hamblin. 1983. Harmonic Charts. Aquarian Press: Wellingborough, page 19. Hamblin was a student of Addey's until he was seduced to the Dark Side of the Force by Geoffrey Dean. (remember the lecture by Nick and me on CSICOP in 103!)

As you can see, with all these methods of assigning orb size, it's really important to spell out your method!

Before we leave aspects, there are several other systems of classification you need to know:

Approaching and Separating: especially in horary and its sister schools of electional and event interpretation, whether an aspect is forming (approaching) or leaving (separating) from partile can be important in interpretation. In horary, only approaching aspects show the future; separating aspects are past. In general, an approaching aspect would be stronger.

Hard and Soft aspects: this refers to the subjective experience of the possessor, and how "easy" the aspect seems. A hard aspect (square or opposition) is generally difficult. A soft aspect (sextile or trine) is easy. The conjunction is situational.

Major and Minor aspects: for a long time, only the major, or ptolemaic aspects were even considered. There was always debate as to whether to call the conjunction an aspect at all, but that is another matter!

It was Johannes Kepler who raised the issue of the minor aspects: other possible aspect ratios which could be interpreted, especially as they were representative of divisions of the circle by relatively small numbers. They can be classified by the division, which also represents their harmonic, using the newer

  • 2nd harmonic: the opposition, a major aspect
  • 3rd harmonic: the trine, a major aspect
  • 4th harmonic: the square and opposition, major aspects
  • 5th harmonic: the quintile (72°) and biquintile (144°), minor aspects
  • 6th harmonic: the sextile and trine, major aspects
  • 7th harmonic: the septile (51.4°), biseptile (102.8°), and triseptile (154.3°), minor aspects
  • 8th harmonic: the square and opposition, major aspects; and the semi-square (45°) and sequiquadrate (135°); both minor aspects
  • 9th harmonic: the novile (40°), binovile (80°), and tetranovile (160°), minor aspects; and trine, a major aspect
  • 10th harmonic: the decile (36°), quintiles (72° and 144°), and tridecile (108°), minor aspects; and opposition, a major aspect
  • 12th harmonic: the semi-sextile (36°) and quincunx (150°), minor aspects; and the third and fourth harmonic major aspects

Burk covers these aspects, differing only from my interpretation here by referring to the quincunx as a major aspect. Many modern astrologers consider the quincunx important enough to rate major aspect status.

Planetary Speed:

As far back as the Babylonians, the speed of a planet was considered an important component of its delineation. Later astrologers did not follow the Babylonian system precisely, but vestiges of these ideas continued, especially in the development of the concept of accidental debility.

As you should recall from lectures on spherical astronomy and Week 2, the conjunction of a planet with the Sun and its opposition to the Sun can be considered extrema of its orbit.

  • When any planet is conjunct the Sun, it is invisible. That is the primary meaning of combust: when any planet is within about 8° of the Sun, it is invisible, hence combust.
  • Planets between 8° and 17° of the exact conjunction with the Sun may or may not be invisible, depending on the brightness of the planet. This zone is called Under the Beams.

The astrological interpretation of these conditions is negative for the planet, but not necessarily for the Sun. From the standpoint of the planet, it’s rather like an eclipse: invisibility means that its expression is muted.

In Hellenistic astrology, however, there is a somewhat additional interpretation relating to the Sun. Because the Sun, like the Moon, is considered royal, it’s considered very bad form for a monarch to be wandering around without attendants. Planets with the Sun are called either Attendants or Spear-bearers, depending on the Englished source, and this is a good thing from the standpoint of the Sun.

Notice that this idea matches up precisely with the way that Medieval monarchs treated their lords. By requiring their lords to spend time “attending” the king, the king made life more expensive for the lord, took the lord away from his own area of greatest strength, and in the mean-time, increased his own strength in the process. The only exception from the standpoint of the planet is cazimi, the 30’ of arc in the “Heart of the Sun.” This is considered very fortunate, and in our Medieval model, this would be like being one of the King’s favorites.

So much for the conjunction. When a planet is opposite the Sun it is, by definition, retrograde. For the inferior planets, one of the two conjunctions can be considered analogous to opposition, since it is also retrograde. While the planet at the conjunction is at its fastest, a planet at opposition can be considered the slowest, although technically, it has negative speed. A slower planet was generally interpreted as less functional than a faster planet through the 17th c.

Both combustion and slow speed were classified as forms of accidental dignity from the Medieval period forward. That they continued to be linked as part of the same cycle is shown by the fact that both conditions were collectively referred to as “imbecilic.”

Lots/Arabic Parts:

Lots or Arabic Parts? Which word you use depends upon which historical period you are studying. The term Lots is applied in the Hellenistic period; after that, the same concept is called the Arabic Parts. These are points arrived at by calculation; they are not physical entities.

The Lots first appear in Hellenistic astrology. At that time, they were developed to aid in the interpretation of houses. This idea came out of the difficulty that every house had/has multiple meanings: so unless all affairs of that house work equally well, or more-or-less in the same way, how does one - for example - distinguish small animals, disease and employees/slaves through the 6th house? Having several Lots (with different calculation schemes) associated with a house "solved" this conundrum, as, later in the Arabic period, the three Triplicity rulers of each house were used to distinguish three major themes within a house.
(c)2006 Lee Lehman