Lunar Astronomy
Moon Phase On Your Birthday
The Moon you were born under, drawn exactly as it appeared — its real illumination, its waxing or waning side, and the sign it travelled through.
Computed from real Sun & Moon positions, not a generic graphic.
Your Birth Moon
Reveal Your Moon
Pick a date to see its true lunar phase, or compare two birth Moons for an honest note on how your inner skies resonate.
The Eight Faces
The Lunar Cycle
The Moon completes one cycle of phases roughly every 29.5 days as it moves around the Earth relative to the Sun.
New Moon
The Moon sits between Earth and Sun, its lit face turned away. A dark sky — traditionally a clean slate for intentions.
Waxing Crescent & First Quarter
Light grows on the right (northern hemisphere). Momentum builds; the half-lit First Quarter is a push-through decision point.
Full Moon
Earth lies between Sun and Moon; the full face is lit and high at midnight. A peak of clarity, feeling, and culmination.
Waning & Last Quarter
Light fades from the right. A season of gratitude, release, and reassessment before the cycle renews at the next New Moon.
How this tool computes your Moon
We take the real geocentric longitudes of the Sun and Moon for your date (VSOP87 for the Sun, a truncated ELP2000 series for the Moon), evaluated at 12:00 UT. The angle between them — the elongation — determines everything: the illuminated fraction is (1 − cos elongation) / 2, and the phase name follows the standard windows around 0°, 90°, 180°, and 270°.
That is genuine astronomy. The same date always gives the same Moon, and for the compatibility mode we never invent a score — we show both real Moons and describe their true angular relationship.