Although the Moon keeps the same face toward Earth, small oscillations called libration let us peek around the edges over time — about 59% of the surface becomes visible. Latitude (N/S) comes from the Moon's axial tilt; longitude (E/W) from its elliptical orbit. The colongitude is the selenographic longitude of the sunrise terminator, used to predict which features cast dramatic shadows.

The hour angle is the Moon's angular distance from your local meridian — 0° means it is due south (transit), negative = east (rising), positive = west (setting). The lunation number (Brown) counts complete lunar cycles since January 1923. The phase angle (0–360°) tracks the Moon's position in its synodic month from new moon (0°) through full (180°) and back.