Natal Moon Phases Explained: The Sun-Moon Cycle at Your Birth

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Your natal Moon phase describes where the Moon was in its monthly cycle with the Sun at the moment you were born. Your Sun sign and Moon sign each describe one body. The phase describes the two of them together: how far the Moon had moved ahead of the Sun since the last New Moon, and whether it was heading towards the Full Moon or away from it.

This page explains how the phase is defined on Astrologist.com, why the direction matters, and where the phase fits in a reading. Working it out from your own chart is covered step by step in how to find your natal Moon phase.

Calculator note: The Astrologist.com birth chart does not calculate or label Moon phases. It shows the Sun and Moon by sign, degree and minute, and the phase described here is worked out by hand from those two positions. Without a birth time, the chart places the Moon at local noon as a date reference only, so a phase read from that position is not established until the whole birth date has been checked.

A cycle between two bodies

The Moon goes round the zodiac in about 27 days, but it catches up with the Sun only about every 29.5 days, because the Sun moves on by roughly a degree a day in the meantime. That catch-up cycle, from one New Moon to the next, is the lunation cycle. Calculated with the same routines as the free chart over 1900 to 2099, one New Moon followed another after 29.27 to 29.83 days, 29.53 on average.

At the New Moon the Moon stands at the same zodiac longitude as the Sun. It then pulls ahead, reaches the point opposite the Sun at the Full Moon, and closes the gap again until the next New Moon. Your natal phase is a snapshot of that cycle.

Measured with direction: Moon minus Sun

Astrologist.com measures the phase with the directed elongation: the Moon's ecliptic longitude minus the Sun's, counted forward in zodiac order and taken modulo 360. The result runs from 0° to just under 360°. Values below 180° mean the Moon is moving away from the Sun (waxing); values from 180° up mean it is coming back towards it (waning).

The direction is the whole point. The ordinary separation between two planets, the one used for aspects, only runs from 0° to 180° and does not say which body is ahead. Two example charts, calculated with the free chart's routines, show why that matters:

• Amsterdam, 9 June 1987, 07:45. Sun 17°52' Gemini, Moon 11°57' Scorpio. The Moon is 144.1° ahead of the Sun: a waxing phase.
• Leeds, 23 November 1983, 14:10. Sun 0°42' Sagittarius, Moon 9°55' Cancer. Here the separation is 140.8°, almost the same as in Amsterdam, but counted forward from the Sun the Moon is 219.2° ahead, so it has already passed the Full Moon: a waning phase.

Read by separation alone, the two charts would look alike. Read by direction, they sit on opposite halves of the cycle.

The eight phases

The cycle is divided into eight equal sectors of 45°, each starting at a multiple of 45°. This eight-phase scheme was popularised by Dane Rudhyar in the mid-20th century, notably in his book The Lunation Cycle, and is a well-established convention for natal phases in modern Western astrology, the one used in these guides.

A value exactly on a boundary belongs to the phase that starts there, so 90°00' counts as First Quarter. Each phase lasted between 3.17 and 4.17 days in the 1900 to 2099 calculation, about 3.7 days on average, because the Moon's speed varies through its orbit. The meanings astrologers attach to the first four are on born under a waxing Moon, and the last four on born under a waning Moon.

Moments and sectors are different things

Calendars and astronomers use "New Moon", "First Quarter", "Full Moon" and "Last Quarter" for single moments: the instants when the elongation is exactly 0°, 90°, 180° and 270°. In the natal scheme above, those names refer to 45° sectors that begin at those moments. Someone born two days after the astronomical Full Moon is still in the Full phase here.

Popular phase names such as "waxing crescent" follow yet another division, based on how much of the Moon looks lit, and some astrologers use only four quarters or centre each phase on its moment. Astrologist.com uses the eight 45° sectors starting at 0° throughout, and states the elongation so that anyone using another convention can convert.

Not the same as a Sun-Moon aspect

A phase and an aspect both come from the Sun and Moon, but they are measured differently. Aspects use the undirected separation with orbs; phases use the directed elongation with fixed sectors and no orb. Every chart has a phase, while in a sample of London noon charts from 1900 to 2099 only 33.2% had a major Sun-Moon aspect within orb. Moon phase vs Sun-Moon aspects sets the two side by side, and the five existing aspect pages, from Sun conjunct Moon to Sun opposite Moon, keep their own focus on the angle itself.

What a phase can add to a reading

Astrologers who use natal phases read them as a background rhythm: whether a person tends to start things, build them, refine them, share them or let them go. It is a broad pattern shared by about one birth in eight, so it works best as a lens on placements you have already read, such as the Sun and Moon signs covered in Sun, Moon and Rising explained. It does not decide anyone's character or future, and a phase description that does not match your experience is simply one that does not fit.

Birth time and the phase

The Moon gains about 10 to 15 degrees on the Sun in a day, so the phase can change during a single date. In London that happened on 27.1% of all dates from 1900 to 2099. A known birth time settles it. Without one, check both ends of the day as described in Moon phase without a birth time.

What the free chart shows

The free birth chart lists the Sun and Moon by sign, degree and minute in the planet table under the wheel. That is all you need for the phase. The chart does not name the phase, so you subtract the two positions yourself, a calculation that takes a minute with the steps on the finding page. If you would like to talk through what your phase might add to the rest of your chart, you can ask the Astrologist.

Related articles

• How to Find Your Natal Moon Phase
• Moon Phase vs Sun-Moon Aspects
• Born Under a Waxing Moon
• Born Under a Waning Moon
• Moon Phase Without a Birth Time
• What Your Moon Sign Means