Method and sources

Sun sign

The Sun's position is calculated from the date and time converted to universal time, with the Bureau des longitudes' VSOP87 theory (Jean Meeus's abridged version), corrected for nutation and aberration: it stays within 0.001° of the Swiss Ephemeris, less than two minutes on the time of a sign change. The zodiac used is the tropical zodiac of Western astrology: twelve 30° sectors counted from the vernal point (spring equinox), unrelated to the current constellations.

Without a birth time, the calculation is done at noon local time: the Sun moves about 1° a day, so the error stays below 0.5°. On the very day of a sign change, both possible signs are shown.

Ascendant

The city is looked up via Open-Meteo's geocoding API (GeoNames data), which provides its coordinates and time zone. Local time is converted to universal time with the IANA time zone database, daylight saving time and historical changes included.

We then calculate the local sidereal time and the obliquity of the ecliptic (Jean Meeus), then the degree of the ecliptic rising on the eastern horizon: λ = atan2(cos θ, −(sin θ·cos ε + tan φ·sin ε)), where θ is local sidereal time, ε the obliquity and φ the latitude. The ascendant changes sign roughly every two hours: an error of a few minutes in the time can move it near a boundary. Beyond the polar circles, the formula can point to the setting degree: the opposite point is then used. The ascendant explained step by step.

Moon, Venus and Mars

The Moon is calculated with Jean Meeus's theory (chap. 47), reduced to its 34 main periodic terms: the difference from the full theory stays around 0.01°. Venus and Mars are calculated from the orbital elements published by the JPL (NASA), valid from 1800 to 2050: Kepler's equation is solved for the planet and for the Earth, light travel time is taken into account, then the position is referred to the vernal point of the date. Compared with the Swiss Ephemeris from 1900 to 2050, they differ by at most 0.03° and 0.06°.

The Moon moves about 13° a day and changes sign every two and a half days. Without a birth time, AstroGramme looks at its position at the start and at the end of the day: if it changed sign that day, both possible signs are shown. The same check is made for Venus and Mars, which are much slower.

Astrological interpretations

The elements (Fire, Earth, Air, Water), modes (cardinal, fixed, mutable) and sign rulers follow the tradition handed down from Ptolemy; the modern rulers (Uranus, Neptune, Pluto) are shown in brackets. The descriptions are written for AstroGramme from these traditional associations: they are portraits, not quotations. The Moon (emotions), Venus (love, tastes) and Mars (action, desire) keep their traditional meanings.

Enneagram

The questionnaire has 9 questions with 4 answers each. Each answer gives 3 points to one type and 1 point to one of its wings (a neighbouring type on the circle). Each type is the main target of 4 answers and the wing of 4 others: no type is favoured by design. The dominant type is the one with the most points; the dominant wing, the best-scoring neighbour. If the top two types end one point apart or less, three tie-break questions follow: each sets a statement from each type against the other (motivation, fear, reaction under pressure) and gives 2 points to the one chosen, nothing if both fit equally.

The basic desires and fears, the wings and the lines of growth (1→7→5→8→2→4→1, 9→3→6→9) and stress (reverse direction) follow the Riso and Hudson model. The three centres (instinctive, feeling, thinking) group types 8-9-1, 2-3-4 and 5-6-7.

The second wing. According to the Enneagram Institute, most people have a dominant wing, but many people in the second half of life say they see their “second wing” develop; the Institute says it does not know whether this is real development or greater self-awareness. Suzanne Stabile also describes a shift from one wing to the other over a lifetime. AstroGramme therefore always shows both wings and adapts the comment from age 40, a threshold we chose for “the second half of life”.

In-depth test

The optional in-depth test has 36 questions: 27 type questions, on the same scale as the short test (3 points to the type, 1 point to a wing), and 9 instinct questions, inserted every three questions. Each type is the main target of 12 answers; each of its two wings receives the secondary point 6 times, which settles the wings much better than the short test.

The instinct questions offer 3 answers, one per instinct: self-preservation (security, comfort, resources), social (place in the group) and sexual (intensity of one-to-one connection). The most chosen instinct gives your subtype, the least chosen your blind spot, following Riso and Hudson's notion of the “instinctual stack”. The 27 subtype portraits are freely inspired by the descriptions of Claudio Naranjo and Beatrice Chestnut; the names are our own adaptations.

Synthesis

The synthesis paragraph is assembled, not generated by an AI: it crosses the element of your Sun with the centre of your Enneagram type (12 written combinations), adds the element of your ascendant, sets the Moon against the Sun and Venus against Mars (same element, kindred or contrasting elements), then the growth path of your type.

Limits

Astrology has no scientific validation: in Shawn Carlson's double-blind study (Nature, 1985), astrologers did no better than chance at matching charts to personality profiles. For the Enneagram, the review by Hook et al. (2021) finds encouraging but still limited results. Our questionnaires, short and in-depth alike, are not validated psychometric tests.

AstroGramme is meant as a mirror for self-reflection, not a verdict.