What Is an Aspect?

Take the zodiac circle from lesson one and place two planets on it. The angular distance between them (60 degrees, 90 degrees, whatever it is) is a plain geometric fact. An aspect is what the traditions call certain privileged values of that angle.

Geometry first

The measurable half of the idea is uncontroversial: positions along the ecliptic can be expressed in degrees, and the separation between two positions is arithmetic. On Astro Gazer these angles are computed by the calculation service from astronomical data; a writer never asserts an angle, and this lesson deliberately calculates none.

The privileged angles themselves have a geometric elegance the tradition noticed early: they divide the circle into equal parts (by two, by three, by four, by six), which is exactly why those numbers and no others became the classical aspect set.^[1]

Meaning second

The interpretive half is doctrine: the claim that planets at such angles 'behold' or 'regard' one another and combine their significations. Hellenistic sources conceived this largely sign to sign: signs a third of the circle apart are in trine, whatever the exact degrees, while later practice, from Lilly's manual to modern software, increasingly measured aspects degree to degree. Ptolemy's Tetrabiblos gives the classical rationale for the configurations.^[2][1][3]

The next lesson walks through the five classical aspects one by one, including the practical question every school answers differently: how close to exact an angle has to be before it counts.