Methodology: how we calculate charts and check birth data

This page describes where the numbers in the charts and articles come from: the source of the birth data, the calculation of planetary positions and the way degrees are written. If something in a chart looks odd, the answer is most likely here.

Chart calculation

Charts are calculated by the AstroWay calculation service using the Swiss Ephemeris; the engine version is shown under every chart. The zodiac is tropical and the house system is Placidus.

A public figure's chart is calculated once, when the profile is added, and stored together with the input data. The page does not call the service when you view it, so the chart cannot change unnoticed. If the birth data changes, the chart is recalculated and the date on the page is updated.

Degrees and orbs

Positions are written in degrees and minutes of a sign: 22°55′ Gemini. Minutes are truncated, not rounded, so 22°55′ means a point between 22°55′ and 22°56′. Aspect orbs are written the same way, which is why a number in an article matches the chart table.

The allowed orb depends on the pair of planets; the table and the reasoning are on the aspect orbs page. Whether an aspect is applying is decided by whether the orb is shrinking or growing at the moment of birth.

Birth data

For every person we give the date, time and place of birth, the time zone in force at that moment and the source. Each source is listed with its title and a link, and what it says about the birth time is explained in the "what is known and what is not" section. The date of our check is at the bottom of the table.

Documents come first: a birth certificate or a hospital record. Then the person's own words or the family's, then biographies. Data from astrological collections is checked against the original source. When a data collector states it holds a birth record but no copy is public, we publish the time marked AA* and name the collector. When sources disagree, every version with its source is listed under "what is known and what is not".

The Rodden rating

The reliability of a birth time is marked on the scale introduced by the astrologer Lois Rodden and widely used by astrological databases:

• AA: from a document, a birth certificate or a record we have seen a copy of;
• AA*: a birth record held by a data collector, with no public copy;
• A: from the person, the family or people close to them. We must find the quote ourselves: in an interview, a book, a post, or quoted word for word by a data collector. An astrologer's retelling without the quote is rated C;
• B: from a biography or an autobiography;
• C: approximate or doubtful, an unknown source or a rounded time;
• DD: conflicting data, several versions with none preferred;
• X: time unknown;
• XX: even the date is in doubt.

Only a time rated AA, AA* or A becomes the main time of a chart. Versions rated B, C or DD and rectified times are mentioned under "what is known and what is not", but no chart is built on them.

When the time is unknown

If the birth time is unknown, the chart is cast for local noon. The planetary positions are still nearly right: in half a day the Moon can move up to 8°, the other planets much less. Houses and the Ascendant are not shown, since they cannot be known without a time, and the page carries a "time unknown" note.

Corrections

If you have a document or a reliable source that contradicts our data, write to us through the contact page and include a link. We check the source, update the data and the chart, and change the date of the check. Who we are and how the texts are written is on the about page.