Orbs of astrological aspects

The word "orb" in astrology is used in two contexts: the orb of a particular aspect and the orb of a particular planet. The orb of an aspect is how far that aspect can be from being exact (refer to "aspects" here if necessary) and still be in effect. Orbs are expressed in degrees of deviation from perfection for that particular aspect. For all aspects, orbs are numerically largest for the Sun and Moon, smaller for the inner planets, and smallest for the outer planets (see the rightmost, upper table on page one of "You and the Universe"). Orbs also decrease as the aspect’s harmonic number increases.

The orb of a planet is the same idea, but it's the difference a particular planet is from being exactly for a particular aspect. Thus a planet can be "in" or "out" of orb if its position falls respectively within or outside of the acceptable deviation (the orb) for being in exact relationship (the aspect) to another planet.

The last header above each aspect in your book "You and the Universe" ends with "orb = o/m," where "o" and "m" stand for numbers that vary. "o" is each aspect’s orb: how far apart two planets in aspect are from being exactly in aspect. When two planets are in exact aspect, say 120° or 180° apart, their orb is said to be 0°.

m is the maximum orb two planets in aspect can have and still be in aspect; m varies from 1° to 12° depending on the aspect. As its orb decreases, an aspect’s strength increases, but its strength also depends on its maximum orb m. An aspect with an orb of 1°, for example, has a much higher strength when m = 12 than when
m = 2 (the fractions in this case are o/12 and o/2). The smaller the fraction o/m, the higher the strength. As you read aspect strength headers in your book, o, the numerator of o/m in the fraction "orb = o/m."

So an aspect’s strength depends on:

• How small the aspect’s orb is: the smaller it (o) is, the greater the aspect’s strength;

• How large the maximum allowable orb is: the larger it (m) is, the greater the strength;

• Whether or not either planet is the Sun or the Moon; aspects involving either (and particularly both) are much more significant.

• Whether or not either planet is "angular" (that is, whether or not it's in the first, fourth, seventh or tenth houses, or conjunct the ascendant, nadir, descendant or midheaven); the closer either planet is to an angle, the greater is the aspect’s strength.