These aspects are the conjunction (approx. 0-10°), sextile (60°), square (90°), trine (120°), and opposition (180°). It is important to note that different astrologers and separate astrological systems/traditional utilize differing orbs (the degree of separation between exactitude) when calculating and using the aspects, though almost all use a larger orb for a conjunction when compared to the other aspects. The major aspects are those that can be used to divide 360 evenly and are divisible by 10 (with the exception of the semi-sextile).
A conjunction is an angle of approximately 0-10°. If one of the bodies is the Sun or Moon, a separation (orb) of approximately 0±10° is considered a conjunction. If neither the Sun or Moon is involved, a conjunction is a separation (orb) of about 0±08° (though different astrologers use different orbs). This is said to be the most powerful aspect, intensifying the effects of the involved planets mutually — and being a major point in the chart. The planets will act together to outside stimulus and act on each other. The essential feature of a conjunction is that each planet brings out a characteristic in accord with its own nature out of the other planet. This may probably be difficult to achieve without the aid of the other planet. This process, however, will also cause each planet involved to lose some of its true characteristics.
Whether the union is to be regarded as "positive" or "negative" depends upon what planets are involved: Venus, Jupiter and the Sun, in any possible combination, is considered the most favourable scenario while the most unfavourable configurations involve Mars, Saturn, and/or the Moon . If the planets are under stress from other configurations, then the conjunction will be said to intensify the stress. When a planet is in very close conjunction to the Sun it is referred to as cazimi; when a planet is moderately close to Sun, it is said to be combust. The Sun and Moon are in conjunction monthly during the New Moon.
A sextile is an angle of 60° (1/6 of the 360° ecliptic, or 1/2 of a trine [120°]). A separation (orb) of 60±04° is considered a sextile. The sextile has been traditionally said to be similar in influence to the trine, but of less significance. It indicates ease of communication between the two elements involved, with compatability and harmony between them, but only provides opportunity, requiring effort to gain its benefits.
A square is an angle of 90° (1/4 of the 360° ecliptic, or 1/2 of an opposition [180°]). A separation (orb) of 90±05° is considered a square. As with the trine and the sextile, in the square, it is usually the outer or superior planet that has an effect on the inner or inferior one. Basically, the square's energy is similar to that of a trine but it is intensified to such an extent that the energy is said to be stressful. The square is said to indicate strain, tension, frustration, inhibitions, disruption and inner conflict. However, it can become a source of energy and activation to a person determined to overcome limitations, presenting challenges to achievement and an opportunity to develop strength of character. The square is also sometimes known as the quartile.
A trine is an angle of 120° (1/3 of the 360° ecliptic). A separation (orb) of 120±04° is considered a trine. The trine indicates harmony, and ease of expression, with the two elements reinforcing each other. The trine is a source of artistic and creative talent, which is innate. The trine has been traditionally assumed to be extremely beneficial, providing ease even if undeserved, but it can be a 'line of least resistance' to a person of weak character. Too many trines are said to make a person weak and unable to cope with adversity. Complacency can also prove to be a problem. Due to the harmony bestowed by the trine, the person may not feel the need to develop the gifts given by this aspect, thus it follows that the person has no need to satisfy a need and supply what is lacking because it is already satisfied from the time of his or her birth.
An opposition is an angle of 180° (1/2 of the 360° ecliptic). A separation (orb) of 180±05° is considered an opposition. Oppositions are said to be the second most powerful aspect. The opposition is indicative of tension, conflict and confrontation, due to the polarity between the two elements involved. Stress arises when one is used over the other, causing an imbalance; but the opposition can work well if the two parts of the aspect are made to complement each other in a synthesis. They are looked on less negatively than in the past, though the opposition is still considered a difficult aspect. The Sun and Moon are in opposition monthly during the Full Moon.
The traditional minor aspects, introduced by the famed astronomer/astrologer Johannes Kepler in the 16th Century AD, were long considered to be of relatively secondary importance, although many modern astrologers are not in agreement with this. These included the quincunx (150°), semisquare (45°), sesquiquadrate (135°), semisextile (30°), quintile (72°), and biquintile (144°).
Astrologers using Cosmobiology and Uranian/Hamburg Astrology work with many more minor aspects then what were used prior 1970, i.e. multiples of 15° (15°, 75°, 105°, & 165°) and multiples of 22.5° (22.5°, 67.5°, 112.5°, & 157.5°).
The quincunx (or inconjunct) is an angle of 150°, which is five-twelfths of the 360° ecliptic. A separation of 150±2° is considered a quincunx. The quincunx is said to be of moderate but somewhat unpredictable influence, bringing strain. It indicates difficulty and stress, due to incompatible elements being forced together. It can mean an area of self neglect in a person's life (especially health), or obligations being forced on a person. This aspect is also sometimes called the inconjunct, though this usage is technically incorrect.
The semi-square is an angle of 45° (1/2 of a square [90°]). A separation of 45±2° is considered a semisquare. This aspect is considered a weaker version of the square and indicates somewhat difficult circumstance. It is sometimes known as the octile or semiquartile.
The sesquiquadrate is an angle of 135° (a square [90°] + a semisquare [45°]). A separation of 135±2° is considered a sesquiquadrate; it indicates somewhat stressful conditions. it is considered similar in influence to the semisquare. The sesquiquadrate is sometimes called a sesquisquare, square-and-a-half, quartile-and-a-half, and/or trioctile.
The semi-sextile is an angle of 30° (1/2 of a sextile [60°]). A separation of 30±2° is considered a semisextile. This aspect signifies a weak strain connected with making decisions, and indicates an area of life where a conscious effort to be positive will have to be made. Alternate names include confinis and inconjunct.
The quintile is an angle of 72°, i.e. the angle for a regular pentagon. A separation of 72±2° is considered a quintile. This aspect is considered somewhat similar to a semisextile (moderately beneficial), but effort is not needed to reap its benefits. Indicates talent and vaguely fortunate circumstances.
The biquintile is an angle of 144° (a quintile [72°] x 2 = 144°). A separation of 144±2° is considered a biquintile. This is considered similar to a quintile.
The Semiquintile also known as a Decile is an angle of 36°. This aspect is said to impart ability to help others .
The Septile is an angle of 51.428571°. It is supposed to be aspected to have irrational relations between its constituent components but confer the hidden underlying nature and deeper destiny of them .
The Novile also known as a Nonagen is an angle of 40°. The novile is said to represent a constriction between the aspects that can be unlocked and used as a catalyst to self-enhancement .
The Binovile is an angle of 80°.
The Biseptile is an angle of 102.857143°. This aspect is considered the externalized septile.
The Triseptile is an angle of 154.285714°.
The Quatronovile also known as a Quadrinovile is an angle of 160°.
The Semi-Decile or Vigintile is an angle of 18°.
The Undecim is 1/11th of a circle or an angle of 32.727272°; in addition there are Biundecim (65.454544°), Triundecim (98.181816°), Quadriundecim (130.90908°) & Quinqueundecim (163.63636°). The Undecim is said be to associated with social consciousness and the ability to reach beyond oneself for help.
The Sesquiquintile or Tridecile an angle of 108°, which is supposed to confer a social creativity or the need for withdrawal and introspection needed for external originality. This aspect is also known as the quintile-and-a-half.
The Quindecile or Johndro is an angle of 165°. Is supposed to be associated with an unrelenting head-strong determination.
The Squine is an angle of 105°, considered a hybrid between a square and a trine.
You have a T-Cross (also called the T-Square) when two planets that make an opposition aspect (180 degrees) are both making a square aspect (90 degrees) to some third planet. Draw lines connecting all three and you have a T.
A Grand Trine is formed when two planets that make a trine aspect (120 degrees) both make another trine aspect to a third planet. If you draw lines connecting all the planets, you get an equilateral triangle.
Sometimes, a fourth planet is opposite one of the Grand Trine planets. That means it will probably make sextiles (60 degree aspects) to the other two Grand Trine planets. If you draw connecting lines on the chart, you get what looks like a Kite formation.
A Yod is formed when two planets make a sextile aspect and a third planet is opposite their mid-point. That third planet must make angles of 150 degrees with the other two. If you drew lines on the chart connecting the planets, you would get a Y-shaped formation that seems to point to one part of the horoscope.
An exact aspect is very brief. This is so because the planets are always in motion. However, an aspect is valid within a certain range of accuracy. This range is called "the maximal orb" of an aspect. Consequently, an opposition is valid when the planets are between 172 and 180 degrees apart. This means that the maximal orb for an opposition is 8 degrees. The same holds for a conjunction that is good up to a distance of 8 degrees. The square has an orb of 7 degrees, the trine 7 degrees, and the sextile 6 degrees. The effect of an aspect is strongest when it is exact. It is weakest when it reaches the orb. For instance, two planets exactly 60 degrees apart are in their strongest mutual aspect, while when 54 or 66 degrees apart, the influence of the aspect is still noticeable, but it is very weak.
In indian astrology, concept of aspects is weak. They lay more stress on yogas and talk in terms of houses. e.g. Gajkesari Yoga exists when jupiter is in 7th house from moon. So when jupiter and moon form angle of 172 to 180 degrees then the results of Gajkesari yoga should be strong.However western principle of orb should equally apply to Indian Yogas.
In life script theory we consider far narrower orbs and some angles which are not major or minor aspects in wester astrology. Basically we identify a pattern of planetry bodies irrespective of houses and attribute results to this pattern. We somtimes call it signatures for a specific type of event.
In our opinion , lots of hard work being done by many researcher's on astrology can really fructify, if they just reduce the orb to 2 degress.