Astronomical sources for the Moon tools

These references define phase terminology, orbital geometry, observer coordinates, and eclipse events. Links lead to the public astronomical or timekeeping authority behind each convention.

Astronomy reference books and observation records on a coastal study desk

Reference authorities

Definitions, ephemerides, and catalogues

United States Naval Observatory: phases of the Moon: Defines principal phases by 0°, 90°, 180°, and 270° excess apparent ecliptic longitude. Read the phase explanation.
NASA/JPL Horizons observer ephemeris: Documents observer ephemerides, coordinate origins, reference planes, apparent quantities, and topocentric output conventions used to interpret distance and position results. Read about JPL Horizons.
NASA GSFC: Moon's orbit and distance: Provides reference definitions and representative center-to-center distances for the Moon's elliptical orbit. Read the Moon orbit reference.
NASA GSFC: lunar eclipse catalogue: Provides event classifications, contact terminology, and a century inventory for comparing global lunar eclipse events. Open the 2001–2100 catalogue.
IANA time zone database: Publishes the named time-zone rules used to interpret local dates and clock times. Open the time-zone database.