The planets in our solar system orbit the sun at different speeds but in more or less the same plane. Relative to the earth,
the planets, the moon and the sun (which together form the astrological planets) make ever-changing
angles to each other, and these angles are easily observed at any point in time from an astrological chart. Astrologers
consider certain angles to have special characteristics that influence the subject of the chart in specific ways. These
special angles are called aspects, and interpretation of the aspects in a chart is an integral part of an astrological reading.
There are five major aspects: conjunction, sextile, square, trine and opposition, corresponding to 0, 60, 90, 120 and 180
degrees respectively. So if Mercury and Saturn are
approximately 120 degrees apart on a chart, then this is termed "Mercury trine Saturn" and interpreted according
to the attributions of the two planets and the influence of the aspect (in this case conferring excellent mental organization,
for example). There are other minor aspects that are sometimes used as well, and aspects may occur between a planet and
any point in a chart. So, for example, "Mercury sextile Ascendant trine Descendant" is meaningful (see the discussion
of houses) and brings an ability to communicate and cooperate if seen in a natal chart.
Some of the minor aspects used from time to time are the semi-sextile (30 degrees), semi-square (45 degrees), quintile (72 degrees),
sesqui-square or sesqui-quadrate (135 degrees), biquintile (144 degrees) and quincunx (150 degrees).
Orbs of Influence
Above, the phrase "approximately 120 degrees apart" was used to define a trine, but just how approximate is approximate?
Well, each aspect has an associated value, called an orb of influence or orb, by which an angle can deviate from the exact
definition of the aspect and still be considered as forming the aspect. For example, a square aspect with an orb of six degrees
means that two planets can be six degrees less than or six degrees greater than 90 degrees apart and still be considered as forming
Varying orb schemes are used by different astrologers. Six degree orbs are common for all the major aspects, and sometimes the
orb is increased to ten degrees if the Sun or Moon are involved. The closer an aspect is to being exact, the stronger its influence.
Applying and Separating Aspects
Aspects are considered to be applying or separating depending on whether the planets involved are moving closer to or further away
from forming the exact aspect. Consideration may be given to this when interpreting a horoscope, with applying aspects having
more influence than separating ones. Some astrologers weight the orb of influence so that a greater orb is allowed for applying
aspects than for separating ones.
Hidden or Disassociated Aspects
There are twelve signs of the zodiac dividing the 360 degrees of an astrological chart, so each sign
occupies exactly 30 degrees. Each aspect is a fixed number of degrees, so when two planets make a particular aspect to each other,
they will be a fixed number of signs apart. Planets in conjunction are in the same sign, planets in sextile aspect are two signs
apart (i.e. there is one sign between the signs containing the planets), planets in square aspect are three signs apart, in trine
aspect four signs apart, and in opposition six signs apart.
However, because orbs of influence are used in determining the aspects, it is possible for this system to break down. Consider
a planet near the beginning of a sign making a major aspect to another planet. As all major aspects are multiples of 30
degrees, this second planet will be near the beginning of another sign a given number of signs away, depending on the aspect.
If an orb of influence is allowed, then this second planet may be several degrees short of the true aspect angle, which
means it may actually be at the end of the sign preceding the one it is expected to be in. In this case the aspect is called
a "hidden" or "disassociated" aspect, and the number of signs between the planets is one less than with
a normal aspect (for conjunctions the planets are in different, adjacent signs).
Aspects that are hidden are usually considered to be weakened, and so less emphasis is placed upon them in the interpretation of
Meanings of the Major Aspects
Two planets are in conjunction when they are approximately 0 degrees apart relative to the earth. This aspect can have a positive
or negative influence depending on the planets involved and other aspects to the conjunction. It is a very potent aspect,
combining and concentrating the energies of the planets involved, causing action and self-expression.
Two planets are in sextile aspect when they are approximately 60 degrees apart relative to the earth.
This is a positive aspect, presenting opportunities, productivity and inspiration.
Two planets are in square aspect when they are approximately 90 degrees apart relative to the earth.
This is a negative aspect, causing tension and highlighting problem areas and weaknesses that have to be dealt with.
Two planets are in trine aspect when they are approximately 120 degrees apart relative to the earth.
This is a very positive aspect, bringing inventiveness, confidence, harmony and increase.
Two planets are in opposition when they are approximately 180 degrees apart relative to the earth.
This is a negative aspect of discord, polarization and separation.