The moon's phases, and what each one is for

By Rhys Calloway

A moon phase is the angle between the Sun and the Moon, nothing more. The traditional use is straightforward: the waxing half, from new to full, suits things meant to grow; the waning half suits things meant to finish, reduce or be let go of. The eight-phase scheme divides each half again, giving every stretch of roughly three and a half days a different job.

What do the moon phases mean?

Phase means position in a cycle, and in astrology the cycle is read as a story with a beginning and an end rather than a set of eight separate moods. The Moon leaves the Sun at the new moon, builds light for two weeks, opposes it at the full, then loses light for two weeks and returns.

What astrologers hold is that the first half favours starting and building, and the second half favours completing, sorting and releasing. That much is ancient and near-universal in the tradition. The finer eight-part division, with a distinct character for each eighth, is twentieth century and much more interpretive. Both are set out below, kept apart.

What is a moon phase, astronomically?

A phase is how much of the Moon's lit half is visible from Earth, which depends entirely on the angular distance between the Moon and the Sun as seen from here. At 0 degrees the Moon is between us and the Sun and shows no lit face. At 180 degrees the Earth sits between them and the whole lit face is turned towards us.

The full cycle, called the synodic month, averages 29.53 days. The Moon moves between 11 and 15 degrees a day against the background sky, averaging about 13 degrees, which is roughly its own apparent width every hour. Each eighth of the cycle covers 45 degrees of separation and lasts a little over three days and sixteen hours.

The four quarter points are also aspects — angular relationships between two bodies, the same ones used everywhere else in a chart. New moon is a Sun–Moon conjunction. First quarter is a waxing square, 90 degrees. Full moon is an opposition, 180 degrees. Last quarter is a waning square.

What is each of the eight phases for?

Phase	Sun–Moon separation	Lasts about	Traditionally read as suiting
New	0°–45°	3 days 16 hrs	Starting something nobody has to see yet. Intentions without commitments. Poor for anything needing visible results fast.
Crescent (waxing)	45°–90°	3 days 16 hrs	Committing resources to the thing you started. The point where a vague plan gets a budget, a date or a first refusal.
First quarter	90°–135°	3 days 16 hrs	Pushing through the first real obstacle. Read as friction rather than failure. Decisions that have been deferred tend to surface here.
Gibbous (waxing)	135°–180°	3 days 16 hrs	Refining, testing, correcting. Not launching. The tradition treats it as the last honest chance to adjust before something becomes public.
Full	180°–225°	3 days 16 hrs	Anything that requires other people to see it. Culmination, meetings, releases, confrontations. Also when the thing you started shows what it actually is.
Disseminating	225°–270°	3 days 16 hrs	Distributing, teaching, telling, following up. Getting value out of what already exists rather than making more.
Last quarter	270°–315°	3 days 16 hrs	Cutting. Deciding what does not continue into the next cycle. Read as a crisis of relevance rather than of effort.
Balsamic	315°–360°	3 days 16 hrs	Stopping. Rest, tidying, endings that need no announcement. The tradition is unusually consistent that this is bad for beginnings and fine for nothing at all.

Two notes on using the table. The boundaries are exact moments, not days, so a phase can turn over at four in the afternoon and the character of the day changes with it. And a phase lasting three and a half days is a wide window by any electional standard — wide enough that it should be the last factor considered, not the first.

Which phases are the pressure points?

The two quarters, because both are squares. A square is a 90-degree aspect, and squares are read throughout astrology as the angle of obstruction: two things that will not ignore each other and cannot easily agree. Traditional astrology counted the square among the malefic aspects for exactly this reason.

First quarter is a waxing square, with the Moon gaining light. It is read as pressure that comes from the thing you started making demands you had not budgeted for. Last quarter is a waning square, the Moon losing light, and is read as pressure to stop — the sense that something has outlived the reason it began.

The full moon gets more attention than either, but its structure is different. An opposition puts two things in plain view of each other. That is why the tradition attaches visibility, exposure and other people to it, rather than difficulty as such.

Where does the eight-phase scheme come from?

The eight-fold division as a system of interpretation is modern, and specifically American. Dane Rudhyar set it out in The Lunation Cycle in 1967, working within the humanistic school he had been building since the 1930s. The names in common use — Crescent, Gibbous, Disseminating, Balsamic — are Rudhyar's vocabulary, and the psychological framing of the cycle as a process of unfolding and returning is his too.

Older astrology divided the lunation differently. Four quarters were standard, and the basic distinction was between increasing and decreasing light. Ptolemy, writing in the second century, connected the Moon's phase to the quality it was thought to impart, setting out four stages rather than two: moistening from new moon to first quarter, heating from first quarter to full, drying from full to last quarter, and cooling from last quarter back round to the new. Nothing in the classical material matches Rudhyar's eight personality types.

Anyone presenting the eight phases as ancient is wrong about the date. The material is useful; it is about sixty years old.

What did older astrologers use the phases for?

Electional astrology, which is the branch concerned with choosing when to begin something. The rule appears in Arabic-language sources, in Guido Bonatti in the thirteenth century, and in William Lilly's Christian Astrology of 1647: elect with the Moon increasing in light for anything you want to grow, and with the Moon decreasing for anything you want to diminish.

The tradition also warned off the moments immediately around the new moon, when the Moon is combust — too close to the Sun to be visible, generally within about 8 degrees, with a wider zone "under the sunbeams" out to roughly 17 degrees. A combust Moon was considered weakened, and elections made under it were held to be obscured or to come to nothing. Lilly treats the Moon's condition in an election as more important than almost anything else in the chart, because the Moon is the fastest body and carries the chart's momentum.

Worth noting that classical electional practice never used phase on its own. Phase was one line in a list that also covered the Moon's sign, its aspects, its speed and the condition of whichever planet ruled the matter in hand.

What is a void-of-course Moon, and does it matter more than the phase?

A void-of-course Moon is a Moon that will make no further major aspect to any planet before it leaves the sign it is currently in. Since the Moon changes sign every a little over two days, these gaps happen constantly — sometimes for minutes, sometimes for the better part of a day.

For timing purposes it matters more than phase, because it is far narrower. Phase gives a window three days wide. A void window has a start time and an end time, often only a few hours apart. Lilly's formulation is the standard one: the Moon is void when she is "not applying to any Planet" while she remains in her sign. The classical reading is that matters begun in that gap do not develop — things stall, or turn out to be less than they looked.

Astrologers disagree on two points. Whether aspects to Uranus, Neptune and Pluto count, since traditional practice had no knowledge of them and some modern practitioners include them, which shortens void periods considerably. And whether the aspect must be exact within the sign or merely within orb when the sign changes, which moves the start time. Any published void-of-course table reflects a choice on both, and the tables do not agree with each other.

Does the moon phase you were born under mean anything?

In modern astrology yes; in traditional astrology it is barely addressed. Rudhyar's system assigns a lifelong temperament to each of the eight birth phases — a Balsamic-born person read as oriented towards endings and transmission, a First Quarter person towards building against resistance, and so on. It is a coherent scheme and widely used, and it entered practice with Jones and Rudhyar in the twentieth century.

What older astrology did with the natal Moon was different. Its sign, its house, its aspects and its speed all carried weight; its distance from the Sun mattered mainly for whether the chart was a day chart or a night chart, and for whether the Moon was combust. The phase itself was not a separate topic.

Someone reading a birth chart will also find that the Sun–Moon angle is already described by other means. A Moon 90 degrees from the Sun is a Moon square the Sun, and that aspect has its own long interpretive history independent of any phase name.