Sagittarius: Jupiter, Mercury in detriment, Fire decans

Its symbol, the centaur archer shooting toward the sky, sums up the temperament attributed to it: aim high and do not settle for the near horizon. You work through enthusiasm and the search for meaning; you need space, projects and ideas that lift you, and freedom matters to you more than almost anything.

• Your strengths: optimism, frankness, generosity, a thirst to learn, an enthusiasm that opens doors.
• Your challenges: excess, impatience, a frankness that is sometimes clumsy, trouble keeping commitments and handling everyday details.

In love, you look for a companion in adventure more than a keeper of routine, and the trap is running off as soon as the bond turns serious. At work, you breathe life into projects: travel, teaching, publishing, law, international work, entrepreneurship. Your lesson: see your ideas through, and take care of the details your momentum skims over.

Ptolemy (Tetrabiblos, book I, chapter 11) places Sagittarius among the four “bicorporeal” signs, with Gemini, Virgo and Pisces: set between the solid signs and those of solstice or equinox, they share, at their end and at their beginning, the properties of two states of the weather. This is the origin of the mutable mode.

Vettius Valens (Anthology, book I, chapter 2) calls it the house of Jupiter, masculine, fiery, bicorporeal and royal, and attributes to those born under it nobility, a sense of justice, greatness of soul and generosity. Lilly (Christian Astrology, book I, chapter 16) describes it as of the fiery triplicity, hot and dry, masculine, diurnal, common or double, “the house and joy of Jupiter”.

Ptolemy (chapter 17) assigns to Jupiter, a temperate planet, two “windy and fecund” signs, Sagittarius and Pisces, in trine to the houses of the luminaries, a harmonious configuration. Modern astrology gave Pisces to Neptune but left Sagittarius to Jupiter: on this sign, AstralPro and tradition agree.

• Domicile: Jupiter, for whom it is the day house in Lilly (book I, chapter 9).
• Detriment: Mercury, ruler of Gemini, the opposite sign. Lilly also puts him in detriment in Sagittarius and Pisces.
• Exaltation and fall: none. None of the seven traditional planets is exalted or in fall in this sign.

Lilly adds an exaltation for the North Node, at 3° Gemini, the opposite sign. AstralPro leaves the nodes outside the dignity system: a North Node in Sagittarius is marked “no essential dignity”. For Mars, the sign offers nothing either. Ptolemy (chapter 18) explains why he does not even have its triplicity: the Fire triangle, although it contains his house of Aries, was assigned to the Sun and Jupiter, because Mars is not of the solar sect; the Sun rules it by day, Jupiter by night. AstralPro uses the same rulers.

AstralPro divides the sign by element: from 0° to 10°, Sagittarius, sub-ruler Jupiter; from 10° to 20°, Aries, sub-ruler Mars; from 20° to 30°, Leo, sub-ruler the Sun. Since Fire has no modern ruler, this sequence is exactly that of the Indian decans reported by al-Biruni (Book of Instruction in the Elements of the Art of Astrology, 1029, §451): Jupiter, Mars, the Sun.

The Chaldean faces differ from it entirely: Mercury, the Moon and Saturn, according to al-Biruni's table. Lilly confirms it degree by degree in his chapters on those planets: the first ten degrees of Sagittarius to Mercury, the next ten to the Moon, the last ten to Saturn. This is the system a Renaissance astrologer would have read; your report, for its part, always writes the decan by element.

The positions table gives each body in Sagittarius its degree, house and dignity: “Domicile” for Jupiter, “Detriment” for Mercury, a dash for the other planets. In chapter I, the decan paragraph of each block names Jupiter, Mars or the Sun as sub-ruler, in a form such as “In the 3rd decan (sub-ruler Sun, Leo)”. In the dominants, the sign feeds Fire and the mutable mode. In the House cusps table, a house that begins in Sagittarius has Jupiter as ruler, and chapter IV, Life Domains, reads that domain through the position of Jupiter.

For Camille Morel, AstralPro's sample chart (fictional data), Sagittarius is occupied by two points, Mars at 3°38' and the North Node at 3°00' (retrograde), both in the 1st house. The sign also holds the cusp of the 2nd house, at 15°40'.

• Mars is peregrine there: none of the four dignities, and no triplicity, since Camille was born at night and nocturnal Fire belongs to Jupiter. He is in the 1st decan, sub-ruler Jupiter, and in Jupiter terms (0-12°).
• The North Node has “no essential dignity”. The two points touch: the Mars-North Node conjunction, at 0°37', is marked “Separating”.
• The 2nd house, that of resources, has Jupiter as ruler, and Jupiter is at 0°50' Scorpio, in the 12th house. He is also the dispositor of Mars.
• Two celestial points are listed as position only: Psyché at 12°30' and Dejanira at 13°39' Sagittarius, in the 1st house.

The sign returns in the progressions chapter: on October 1, 2026, Camille's progressed Sun is at 25°13' Sagittarius, and her progressed Ascendant, at 9°17' Sagittarius, has changed sign compared with the natal chart.