Methodology

otldr publishes structured facts, so the way those facts are produced matters as much as the facts themselves. This page describes how the reference pages on this site and across the network are built.

Where the numbers come from

Astronomical figures — planetary positions, retrograde stations, Moon phases, sign ingresses — are computed, not copied. We use the astronomy-engine library, which implements the VSOP87 planetary theory and the ELP-2000 lunar theory, the same models used in professional ephemerides. Asteroid positions (Ceres, Pallas, Juno, Vesta, Chiron) are computed with the Swiss Ephemeris, the reference implementation used across the field.

A retrograde “station,” for example, is found by scanning a body’s apparent ecliptic-longitude velocity and locating the instant it crosses zero — not by transcribing a date from another website. Times are reported in UTC and rounded to the stated precision.

Reference (non-computed) facts

Definitional facts — the element and ruling planet of a sign, the classification of a planet, the meaning of a phase name — are taken from established references (NASA, the IAU, Encyclopaedia Britannica, Astrodienst) and cited on each page. Where a topic has more than one accepted convention, such as classical versus modern planetary rulers, we show both rather than pick one.

Sourcing and dating

Every reference page ends with a Sources list and a “facts verified on” date. The date records when we last checked the page against those sources, so you can judge how current it is. When we revise the facts, we update the date.

What we do not do

We do not publish predictions, horoscopes, rankings, or star ratings, and we do not present interpretation as fact. Astrological meaning is labelled as a symbolic tradition, kept separate from the measured astronomy. See our editorial standards for the full policy.

Questions about how a specific figure was produced? Contact us — otldr is operated independently.