Astrology Investigation Tool

This page was last modified on Tuesday, November 04, 2003

a highly interactive astrology program for the Macintosh.
Arabic Part
a Zodiac point derived from 3 other points. In general, this calculation is of the form A+(B-C). For example, the Part of Plays is Ascendant + (Venus - Mars). Points are sometimes derived from other chart information, such as "Ruler of the 8th House." There are many, many Arabic parts. AIT calculates dozens of them, as well as the aspects other chart objects make to them. Some Arabic parts are calculated differently depending on whether the chart is a Day or Night chart; AIT takes this into account where appropriate. The Part of Fortune (or Pars Fortuna) is an example. In a Day chart, it's Ascendant + (Moon - Sun), while in a night chart, it's Ascendant + (Sun - Moon).
Aspect Name Angle Calculation
Conjunct 0 0
Semisextile 30 (1*360)/12
Semisquare 45 (1*360)/8
Sextile 60 (1*360)/6
Quintile 72 (1*360)/5
Square 90 (1*360)/4
Trine 120 (1*360)/3
Sesquiquadrate 135 (3*360)/8
Biquintile 144 (2*360)/5
Quincunx 150 (5*360)/12
Opposite 180 (1*360)/2
Semiquintile 36 (1*360)/10
Septile 51.43 (1*360)/7
Novile 40 (1*360)/9
Binovile 80 (2*360)/9
Biseptile 102.86 (2*360)/7
Triseptile 154.28 (3*360)/7
Quatronovile 160 (4*360)/9
Two objects are in aspect when the difference between their positions falls on or near specific values. The fast moving object (based on average daily motion) is usually referred to as the aspector, and the object being aspected is the aspectee. When calculating aspects between a transit chart and a natal chart, the transiting item is always considered the aspector. Aspects need not be exact; each has an orb of influence (usually just the term orb is used). The orb is based on the specific aspect. The orb for a conjunction (two objects at the same degree of a sign) is usually wider than the orb for a square (two objects 90 degrees apart). The interpretation of an aspect must take into account not only the angle, but also the nature of the planets, the signs, and the house positions of the objects. A conjunction, for example draws part of its generic meaning from both objects being in the same sign. If both objects aren't in the "right" sign for the type of aspect, the aspect is said to be "dissociate" and it is frequently interpreted as being less significant. When drawing aspect lines between objects, AIT indicates Dissociate aspects by a dotted line.

Aspects are also said to be applying or separating, depending upon whether the aspect is becoming more or less exact. All things being equal, applying aspects are said to be stronger. Whereas applying/separating describes the angle, Approaching/Departing describes the objects. Approaching means one object is moving toward the other, while departing means its moving away. AIT indicates both the approaching/departing status and the applying/separating status of aspects. Inclining and declining are also used as synonyms for applying and separating.

As if that's not enough to consider, many of the aspects also have opening and closing varieties. Planets in normal motion (not retrograde) move counterclockwise around the chart, proceeding in order through the signs. A planet reaches one square, the opening square, when it is 90 from the aspectee. As it transits, it squares our aspectee again at 270, the closing square.

Planets usually don't travel precisely along the ecliptic; they may appear above or below it. This distance is called declination. In addition to aspects of longitude, there are also aspects of declination. Planets are Parallel when their declinations are within orb (usually one degree) on the same side of the ecliptic, and Contraparallel when they are in orb (also one degree) on opposite sides of the ecliptic. A longitudinal aspect of two planets is often said to be significantly enhanced if they are also in aspect by declination. AIT calculates and displays aspects of declination as well as those of longitude. The associated table lists the names of many aspects. Those in italic are less commonly used. The most commonly used aspects certainly are those based on multiples of 30 degrees. Conjunction (0), Semisextile (30), Sextile (60), Square (90), Trine (120), Quincunx (150), and Opposition (180).

An aspectarian is a table whose cells display the aspect made between the objects represented by the cell's row and column. The aspect may be indicated by the glyph for that aspect. The orb of the aspect may also be indicated. AIT allows the display of aspects to be filtered so that only aspects of certain types are displayed. AIT also allows control over the rows and columns in the table. For individual aspectarians, such as the one for a Natal chart, only half of a grid is used since all aspects are within one set of objects.
A composite chart is a chart mathematically derived from two or more charts. Although some references describe a composite chart as the average between a group of charts, that description is misleading. As the number of charts in a composite increases, a composite calculated as an average would tend toward 180 degrees (0 Libra). The manner in which AIT calculates a composite chart is similar to putting weights on the rim of a balanced wheel, and then measuring which way the wheel tilts. For two charts, this is the same as an average, but for more than two, it allows an accurate composite to be calculated.
The dispositor of a planet is the planet that rules the sign in which the planet is posited, or located. For example, since Venus is considered to be the ruler of the sign Taurus, Venus disposits -- is the dispositor of -- any planet located in Taurus.
The Ecliptic is the apparent path followed by the sun as the earth rotates. Eclipses occur when the sun and moon converge on this path.
Influence Graph
An influence graph shows the effect transiting objects have on objects within the reference chart. Objects within orb of aspecting other objects get higher scores depending on the type of aspect and how close the aspects are to exact. These scores are tallied and drawn as a graph. Since aspects are frequently classified as "hard/challenging" and "soft/easy," AIT separates aspects into two groups, and shows the first group's scores as red and those of the second as green.

Depending on the time period being measured, only the objects that have significant average daily motion over that period are used. For example, in a daily influence graph, planets such as Neptune and Pluto move very little, so they are not used in the calculation. On the other hand, points such as the Ascendant and Midheaven cover the entire Zodiac in a day, so they are not used in a monthly or yearly influence graph.

Another type of influence graph can be displayed within the hub of a wheel chart. It indicates the relative strength of aspects for every point -- actually fractions of a degree -- in the zodiac. AIT sometimes refers to this as the Sensitivity Graph, but, since it looks like a blob, it's also called a blob chart.

Retrograde Motion
Because the earth revolves around the sun at a different speed and distance from other planets, it's possible for other planets to appear to move backward as seen from the earth. This backward motion is called retrograde motion. The moon and sun are never retrograde in a horoscope. A retrograde planet is often interpreted differently from a direct planet.
Signature and Sub-signature
A chart signature is calculated by counting the number of planets in each of the elements and modalities. For example, if a chart has more planets in Mutable signs, and more planets in Earth signs, then the signature is the Mutable-Earth sign, or Virgo. Subsignature is determined by house instead of sign. Each house is associated with a sign (1=Aries, 2=Taurus, etc.), each element is associated with a life area, and each modality (Cardinal/Fixed/Mutable) can be associated with angularity (Angular/Succedent/Cadent). Not all horoscopes have signatures or subsignatures. A horoscope can have a subsignature without having a signature.
A synastry chart is a chart that displays the relationship between two charts. In a Synastry Aspectarian, the aspects between the planets of each chart are displayed. In a Synastry wheel, the placement of the secondary chart's points are shown within the houses of the primary chart.
Tropical Astrology
In Tropical Astrology (the type most-commonly practiced in the Western World), the signs of the zodiac are related to the seasons rather than the constellations. The Ecliptic longitude of the Sun at the first moment of Spring, the Vernal Equinox, is 0 Aries.

This page is Copyright 2000 Brad Pettit, All Rights Reserved