How are New Moon, Full Moon, and quarter phases calculated?
Lunations are found by solving for declared Sun–Moon angular separations: conjunction, opposition, and the two quadratures. The event record needs a time scale, ephemeris, coordinate convention, root tolerance, and handling for the angular wrap. A phase timestamp is astronomical geometry, not a prediction.
Direct answer
Lunations are found by solving for declared Sun–Moon angular separations: conjunction, opposition, and the two quadratures. The event record needs a time scale, ephemeris, coordinate convention, root tolerance, and handling for the angular wrap. A phase timestamp is astronomical geometry, not a prediction.
Practical use
What to do with this answer
Search for the target elongation in a bounded interval, normalize angular difference consistently, and retain the refined UTC instant and uncertainty. Keep phase events separate from sunrise-based calendrical day labels.
Distinctions to preserve
- Exact angular event versus named civil day
- Conjunction versus visibility of the lunar crescent
- Astronomical phase versus interpretive rule
Limitations
- A New Moon instant is not the same as first visible crescent.
- Calendar labels depend on additional location and day-boundary conventions.
Authority graph
Which existing contracts carry the answer
These linked pages carry the underlying definition, method, or tradition record and its own sources. This page preserves their boundaries rather than becoming a new source of independent authority.
New Moon calculation reference →
Establishes: The New Moon is defined by a Sun–Moon phase-angle condition centered on 0°. A New Moon is not automatically a solar eclipse; eclipse geometry also requires suitable lunar latitude and observer alignment.
Boundary: The New Moon does not establish a beginning, culmination, crisis, release, or event outcome, and it is not evidence that a chart predicts reality.
Full Moon calculation reference →
Establishes: The Full Moon is defined by a Sun–Moon phase-angle condition centered on 180°. A Full Moon is not automatically a lunar eclipse; most pass north or south of Earth’s shadow.
Boundary: The Full Moon does not establish a beginning, culmination, crisis, release, or event outcome, and it is not evidence that a chart predicts reality.
Tithi calculation →
Establishes: A tithi is one 12° interval of normalized geocentric Moon-minus-Sun ecliptic longitude, counted through waxing and waning halves.
Boundary: A calculated tithi does not establish that an activity is favorable.
Equivalent questions
These query forms resolve to this same answer identity; they are not separate claims.
- How is a New Moon time calculated?
- What angle defines a Full Moon?
- Is tithi the same as Moon phase?
- How are lunar quarters found?
Non-claim
This answer is a method or tradition description. It is not a personalized reading and does not certify predictive validity, causation, medical outcomes, legal status, investment value, or guaranteed events.