Question 1

What are the major aspects in classical astrology?

Accepted Answer

The five major or Ptolemaic aspects are the conjunction (0 degrees, sharing a sign), the sextile (60 degrees, two signs apart), the square (90 degrees, three signs apart), the trine (120 degrees, four signs apart) and the opposition (180 degrees, six signs apart). They are called Ptolemaic because they appear together in Ptolemy's Tetrabiblos (Book I, chapter 13) where he derives them from the harmonic divisions of the circle. Conjunctions and oppositions are neutral in their nature but emphasize the planets involved; trines and sextiles are considered easy or beneficial; squares are considered tense or challenging.

Question 2

What is an orb of aspect and how is it determined?

Accepted Answer

An orb is the maximum permissible deviation from the exact aspect angle within which the aspect is still considered effective: an opposition with an orb of seven degrees, for example, is counted as operative anywhere from 173 to 187 degrees of separation. Classical astrologers assigned individual orbs to each planet rather than to the aspect itself - the Sun and Moon receiving the largest orbs (typically 15-12 degrees) and Mercury and Mars the smallest (7-8 degrees) - so that the orb of an aspect between two planets was the average of their personal orbs. Modern practice often uses smaller, aspect-based orbs of 6-10 degrees for major aspects and 2-3 degrees for minor aspects.

Question 3

What is the difference between major and minor aspects?

Accepted Answer

Major aspects are the five Ptolemaic aspects derived from divisions of the circle by 1, 2, 3, 4 and 6 - the conjunction, opposition, trine, square and sextile - and are considered the strongest and most reliable in classical astrology. Minor aspects are derived from divisions by 5, 8, 9, 10, 12 and so on, including the quintile (72 degrees), semi-square (45 degrees), sesquiquadrate (135 degrees), quincunx or inconjunct (150 degrees) and semi-sextile (30 degrees). Johannes Kepler systematically introduced minor aspects in the seventeenth century on the basis of musical harmonic theory, and they have been further developed in twentieth-century harmonic and cosmobiological astrology.

Question 4

What is a separating versus an applying aspect?

Accepted Answer

An applying aspect is one in which the faster-moving planet is moving toward exactness with the slower planet, while a separating aspect is one in which the faster planet has already passed exactness and is moving away. In horary and electional astrology this distinction is decisive: applying aspects describe events that are about to happen, while separating aspects describe events that have just occurred. In natal astrology, applying aspects are generally considered more dynamic and consequential, while separating aspects describe established conditions or completed processes.

Question 5

Why does sign-based (whole-sign) aspect doctrine differ from degree-based aspects?

Accepted Answer

The Hellenistic tradition, especially Vettius Valens and Antiochus of Athens, treated aspects primarily as relations between whole signs: any planet in Aries was in trine to any planet in Leo or Sagittarius regardless of degree, because Aries, Leo and Sagittarius are the three fire signs. Degree-based orbs were a later refinement that determined the strength of an aspect within the sign-based framework. Modern Western astrology, following the medieval and Renaissance synthesis, generally privileges degree-based aspects with tight orbs, but the contemporary Hellenistic revival has restored sign-based aspect doctrine as the foundational layer, with orb-based aspects added to refine timing and intensity.

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