orbs of aspects in astrology

The "orb" of an aspect is how far that aspect can be from exact and still be in effect (see the 5th and 6th columns in the table below or "aspects" if necessary). If two planets are 92° apart, for example, they are said to be in a 90° aspect (a square) with a 2° orb; if 183° apart, they are in a 180° aspect (opposition) with a 3° orb. Orbs are expressed in degrees of deviation from perfection for an aspect. Orbs are largest for the Sun and Moon, smaller for the inner planets, and smallest for the outer planets. Orbs also decrease as an aspect’s harmonic number (first column below) increases.

harm- onic #	Aspect name	angle	fraction of a circle	orb: Sun & moon	orb: planets	aspect description
1	conjunction	0°, 360°	1/1	12°	11°	power, intensity, emphasis; harmonious or inharmonious depending on the energies of the planets involved
2	opposition	180°	1/2	12°	11°	change, polarity, awareness, objectivity, a particular style of relating; symbolizes a conflict between an internal energy and an apparently external one that one fails to see in oneself and projects onto the world; signifies others we bring into our life to externalize unconscious or rejected aspects of our being.
3	trine	120°	1/3	8°	7° 30'	harmony, ease, gifts, stability, creativity; often denotes inertia
4	square	90°	1/4	8°	7° 30'	obstacles & challenge creating dynamic inner tension leading to conflict & change; planets in square work at cross-purposes and resist, test & limit each other. Their energies are released when the aspect is resolved; not as exteriorized as opposition.
5	quintile	72°	1/5	2°	2°	the bringing together of the male and female within an individual, thus indicating marriage, creativity, and one’s art
5	biquintile	144°	2/5	2°	2°	same as the quintile
6	sextile	60°	1/6	5°	4° 30'	opportunity; unlike the trine, the sextile needs a little push from the will to activate its natural harmony
7	septile	51° 25.7'	1/7	1° 30'	1° 30'	receptivity to inspiration, sacred & religious matters, creativity, children
7	biseptile	102°51.4'	2/7	1° 30'	1° 30'	same as the septile
7	triseptile	154°17.1'	3/7	1° 30'	1° 30'	same as the septile
8	semisquare	45°	1/8	2° 30'	2°	half square; challenge and resistance; like square but weaker
8	sesquiquadrate	135°	3/8	2° 30'	2°	similar to the semisquare: crisis, resistance to challenge
9	novile	40°	1/9	1°	1°
10	decile	36°	1/10	1°	1°
12	semisextile	30°	1/12	2°	1° 30'	similar to the quincunx
12	quincunx	150°	5/12	2° 30'	2°	unites signs with no natural relationship or connection to each other; discord, necessity for adjustment, or a forced choice between inharmonious conditions.

There are actually two usages of the word "orb": the actual orb of the two planets in aspect: the planetary orb, and the theoretical maximum orb of that aspect: the aspect's orb. If for example the Sun and the Moon are 177° apart—as in the book header below—they are in opposition (180°) with an orb of 3°. So 3° is the orb of that particular Sun-Moon opposition. But the opposition aspect itself has a (maximum allowable) orb of 8° to 12° depending on the planets involved and the decision of the interpreting astrologer as to what its maximum allowable orb should be. This last point is a bone of contention among astrologers.

Both usages of the word "orb" are employed in determining your aspects' strengths in the headers above each interpreted aspect in You and the Universe. The "Strength" header (above) lives up to its name; it computes the strength of each of your aspects based on both the (actual) planetary and the (theoretical) aspect orbs. Notice that it ends with "orb = o/m." "o" is the first usage of the word "orb" above: how far apart the two planets in aspect actually are from being exactly in that aspect. In the example above the Sun and Moon are 177° apart, so their actual orb is 3°. But as an astrologer I believe that an opposition between the Sun and the Moon can be as far as 12° (the daily movement of the Moon) from 180° for the Sun and Moon to still be considered opposed. This is my maximum allowable orb for a Sun-Moon opposition. So my "m" for this aspect is 12. In this case, o/m is 3°/12°, and because 3° is significantly less than 12°—the two planets have a long way to go before they are no longer in opposition—this is a strong opposition. The maximum orb m for the first 12 aspects is given in columns 5 and 6 in the table above; it varies from 1° to 12° depending on the aspect and the astrologer.

As its orb decreases, an aspect’s strength increases, but its strength also depends on its maximum allowable orb m. As an aspect's actual orb o approaches its maximum allowable orb m, the strength of that aspect diminishes, and when o reaches m the aspect is considered no longer in effect and its strength is 0.

The higher m is (indicating major aspects like a conjunction, opposition, trine or square), the stronger the aspect for any actual orb between planets. Consider for example a 3° orb. A 177° Sun-Moon opposition (maximum orb m=12°) with a 3° orb is stronger than a 123° trine (m=8°), and much stronger than a 57° sextile (m=5°). In fact, two planets in a 48° semisquare (3° orb) are not actually in semisquare because they are outside the maximum allowable orb for a semisquare. Maximum allowable orbs vary with the astrologer. The one's in the table above are the ones that have best mirrored reality for me over the years.

So an aspect’s strength depends on:

• How small the aspect’s orb is: the smaller it (o) is, the greater the aspect’s strength;

• How large the maximum allowable orb is: the larger it (m) is, the greater the strength;

• Whether or not either planet is the Sun or the Moon; aspects involving either (and particularly both) are much more significant.

• Whether or not either planet is "angular" (that is, whether or not it's in the first, fourth, seventh or tenth houses, or conjunct the ascendant, nadir, descendant or midheaven); the closer either planet is to an angle, the greater is the aspect’s strength.

• Independent of the aspect, the closer a planet is to an angle the stronger that planet's influence is in a chart. When a planet is within 2° of an angle it can easily become the most significant planet in the chart. In this regard the angles from strongest to weakest are: ascendant (first house cusp), midheaven or MC (tenth house cusp), descendant (seventh house cusp), and lastly the nadir or IC (fourth house cusp).

Orbs of astrological aspects