See also: retrograde motion

The angular relationships between the planets in a horoscope, measured as angles within the ecliptic circle, are termed “aspects”. Usually this includes angles to the ascendant and MC. Only certain angular relationships are regarded as aspects, and these are said to have intrinsic qualities – they are said to be “harmonic”, “dynamic” or “neutral”. These relationships influence how the planets work together. There is also a certain amount of “play”, which means that an aspect is said to “work” or be operative within a few degrees either way of being exact. This margin of “play” is defined by the orbs. (see below) 

Here are some of the major aspects:

Conjunction - 0° 
The conjunction tends to be a harmonious aspect. Its quality depends greatly on the planets involved, as well as on how close the aspect is. For example, a conjunction between the Sun and Mercury is generally regarded as harmonious. If, however, the distance between them is less than a few degrees, Mercury is said to be “burnt” or “in combustion”, with corresponding results. In general, the conjunction shows an immediate connection which usually works in one way or another. 

Opposition - 180° 
Although the opposition is generally regarded as “disharmonious” or dynamic, it often has quite a motivating and energizing effect. Here too, the quality of the aspect depends on the planets involved, and on what one makes of it. On the whole, an opposition between two planets creates tension between them, often with positive results. 

Square - 90° 
The square is regarded as a disharmonious aspect, the planets involved seem to be “blocked”. The problems that arise from the square keep on turning up, like a bad penny. The difficulty lies in trying to reconcile two forces that are trying to move in completely different directions. Usually this takes the form of desires and needs which are mutually exclusive. 

Trine - 120° 
The trine is a harmonious aspect, the planets involved work together in a complementary fashion, enriching one another. Trines show where our natural talents lie, whether we actually make use of them or not is up to us. 

Besides the major aspects mentioned above, there are also quite a number of “minor aspects”. Most of these are subdivisions of the major aspects. The minor aspects add depth and detail to the general picture. The orbs permitted for the minor aspects are much smaller than those used for the major aspects. (see table below) 
The most common minor aspects are 
 

Orbs

Orbs for  Astrodienst chart drawing type 2.A