Astrology tools for birth charts, transits, Vedic analysis, and astronomical calculations.
Captured live from the server via tools/list.
natal_chart
A person's birth chart. Requires their exact birth date+time and birthplace (all three: date, lat, lon). Use this — not current_sky — whenever the question is about someone's natal/birth chart. Returns 13 bodies (sun–pluto, chiron, nodes) with sign, house, retrograde, speed; ASC/MC; cusps; major aspects with orb, applying/separating phase, and strength (1=exact). Vs Swiss Ephemeris (1850–2150): Sun–Saturn ≤1″, Uranus ≤1.9″, Neptune ≤4.6″, Moon ≤2.5″, Pluto ≤3.4″ (Chebyshev pack), Chiron ≤1″, mean node ≤1″, true node ≤ 1′ vs SE's built-in ephemeris.
Parameters (5)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
house_systemstring
House system (default placidus). Case- and spacing-insensitive; valid: placidus, whole_sign, equal, porphyry, koch, regiomontanus, campanus, alcabitius, morinus, meridian, polich_page, vehlow (aliases like "whole sign" also work).
zodiacstring
tropical (default) or sidereal:<ayanamsa>
current_sky
The sky at a moment and place — not tied to any person. Use for "what's the sky/transits right now" or the chart of a non-birth event. Date defaults to now; lat/lon default to 0,0 (geocentric on the equator at the prime meridian), where houses and ASC/MC are nominal — pass a real location if houses matter. For a specific person's birth chart use natal_chart instead. Returns positions, houses, retrogrades, aspects.
Parameters (5)
datestring
UTC ISO date-time (convert from local first); omit for now
latnumber
Latitude, north positive; default 0 makes houses nominal
lonnumber
Longitude, EAST positive (Americas are negative); default 0 makes houses nominal
house_systemstring
House system (default placidus). Case- and spacing-insensitive; valid: placidus, whole_sign, equal, porphyry, koch, regiomontanus, campanus, alcabitius, morinus, meridian, polich_page, vehlow (aliases like "whole sign" also work).
zodiacstring
tropical (default) or sidereal:<ayanamsa>
sky_view
Where the visible bodies land in a framed photo of the sky, for an image prompt. Give a place, a moment, an aim (compass direction and altitude), a lens, and an image size; get each in-frame body's pixel position, apparent size, brightness, the Moon's phase orientation, a sky-state summary (twilight, limiting magnitude, horizon row), the bright bodies just outside the frame, a ready-to-use prompt, and a machine-readable `renderPlan` (a body-free background-plate prompt plus the computed layers to composite locally, for a hybrid render pipeline). Caelus computes the geometry and photometry; it does NOT render the image. For "at sunset", first find the set time with sky_events, then pass it as date.
Parameters (14)
datestring
UTC ISO date-time (convert from local first); omit for now
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
elevation_mnumber
Eye height above ground in meters (e.g. 9 for a third-floor window)
azimuthnumber | stringrequired
Center compass direction: degrees from true north (east positive) or a 16-point name like "W" or "WNW"
altitudenumber
Center altitude in degrees: 0 looks at the horizon, positive tilts up
lensstring
Lens preset; sets field of view and projection (ultrawide is fisheye, the rest rectilinear)
widthinteger
Output image width in pixels
heightinteger
Output image height in pixels
bortleinteger
Dark-sky class, 1 (pristine) to 9 (inner city). Sets the night naked-eye limit and drives background star density and Milky Way visibility. Omit for a suburban default
deep_fieldboolean
Pin the complete deep naked-eye star field (thousands of stars at exact pixels) instead of the bright catalog. Larger response; great for control images
overlaysarray
Reference-frame overlays to project (annotations, not photoreal): the ecliptic line, the zodiac signs, house cusps and angles, and constellation figures. Exact pixels returned in `overlays`
include_starsboolean
Include bright catalog stars when a star catalog is loaded
max_star_magnumber
Brightest-magnitude cutoff for stars (smaller is brighter); default 2.5, or the limiting magnitude when bortle is set
sky_view_sequence
A time sequence of sky frames for an animation: the same place, aim, and lens stepped through time. Returns a compact per-frame timeline (instant, twilight, Sun/Moon altitude, Moon phase + bright-limb, whether the Milky Way is in frame) plus the fixed celestial pole and the sky's sidereal rotation per frame. Each frame's full pixel-accurate spec comes from calling sky_view at that instant; this tool plans the timeline. Use for sunset-to-night transitions, star-trail planning, or Moon-phase progressions.
Parameters (11)
datestring
First frame, UTC ISO date-time; omit for now
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
azimuthnumber | stringrequired
Center direction: degrees from true north or a compass name like "W"
altitudenumber
Center altitude in degrees
lensstring
framesintegerrequired
Number of frames (2-60)
step_minutesnumberrequired
Minutes between frames
bortleinteger
Dark-sky class 1-9
widthinteger
heightinteger
synthetic_validate
Check an authored synthetic celestial system for ill-defined inputs: duplicate body ids, non-positive periods, out-of-range eccentricity, or a dangling observer. Returns `impossible` and a list of problems — the same honesty pattern as compileForm.
Parameters (1)
systemobjectrequired
synthetic_positions
Positions of every body in an authored synthetic system at one instant. Three body modes: `placement` (fixed longitude), `periodic` (uniform motion), `kepler` (constant elements). With `observer` set on the system, positions are geocentric/apparent from that body (outer bodies can show retrograde). Pass `t_days` for abstract day units, or `date` (UT ISO) when body `epoch` values are Julian Days. Returns speed and retrograde per body.
Parameters (3)
systemobjectrequired
datestring
UT instant as ISO 8601; used as t when t_days is omitted
t_daysnumber
Time in the same day units as each body's periodDays/epoch (abstract world frame)
synthetic_sky_view
Sky View for a mix of real and synthetic bodies: register the authored system on an ephemeral engine, then frame the visible sky like sky_view. Synthetic bodies can carry render attributes (sizeDeg, magnitude, color) that flow into the pixel spec and prompt. Real Sun/Moon/planets stay for twilight and context unless omitted from `bodies`.
Parameters (13)
systemobjectrequired
datestring
UTC ISO date-time; omit for now
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
elevation_mnumber
Eye height above ground in meters
azimuthnumber | stringrequired
Center direction: degrees from true north or a compass name
altitudenumber
Center altitude in degrees
lensstring
widthinteger
heightinteger
bortleinteger
bodiesarray
Body ids to draw; defaults to Sun, Moon, planets, and every synthetic body
include_starsboolean
Include catalog stars (usually off for fictional skies)
transits
Transiting planets vs natal chart: aspects within orb (applying/separating), natal house per transiting body.
Parameters (7)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
transit_datestring
UTC ISO date-time of transit moment (convert from local first); omit for now
orbnumber
Max orb in degrees
house_systemstring
House system (default placidus). Case- and spacing-insensitive; valid: placidus, whole_sign, equal, porphyry, koch, regiomontanus, campanus, alcabitius, morinus, meridian, polich_page, vehlow (aliases like "whole sign" also work).
zodiacstring
tropical (default) or sidereal:<ayanamsa>
synastry
Compare two people's birth charts: inter-chart aspects with orbs, house overlays both ways, plus ranked citable fact atoms and a ready `brief` (synastry/composite ids for auditCitations). Each person needs date+lat+lon. House overlays always use Placidus (not configurable here).
Parameters (4)
aobjectrequired
Person A birth data (UTC date, lat, lon)
bobjectrequired
Person B birth data (UTC date, lat, lon)
orbnumber
Max orb in degrees
zodiacstring
tropical (default) or sidereal:<ayanamsa>
find_aspect_dates
Exact dates a transiting body makes an aspect, within a range: to a fixed longitude OR to another transiting body. Provide exactly one of target_lon / target_body. Includes retrograde re-hits. Body names are snake_case (mean_node, true_node).
Parameters (7)
bodystringrequired
Transiting body (snake_case, e.g. saturn, true_node)
aspectstringrequired
target_lonnumber
Fixed natal longitude in degrees. Provide this OR target_body, not both.
target_bodystring
Another transiting body. Provide this OR target_lon, not both.
startstringrequired
UTC ISO start date (convert from local first)
endstringrequired
UTC ISO end date (convert from local first); range <= 50 years
zodiacstring
Zodiac for body and target_lon longitudes; tropical (default) or sidereal:<ayanamsa>
rectification_grid
Rectification sweep: ASC/MC at each step across a window of UTC hours on one date, with ASC sign-change times. Use when the birth time is unknown and you want candidate times. The sweep runs over window_start_hour..window_end_hour (UTC hours of the given date); the date's time portion is ignored.
Parameters (6)
datestringrequired
Birth DATE (UTC) as ISO; only the calendar date is used, the time portion is ignored (the window_*_hour fields set the times swept)
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
window_start_hournumber
First UTC hour of the date to sweep
window_end_hournumber
Last UTC hour of the date to sweep
step_minutesnumber
Minutes between grid rows
sky_events
Sky events in a UTC date range: rise/set/meridian transits (need lat+lon+body), lunar phases (new/quarters/full), solar and lunar eclipses, stations (body turns retrograde/direct; needs body), zodiac degree crossings (needs body + target_lon). Solar eclipses report global circumstances (type, magnitude, gamma) plus the greatest-eclipse location and path width; add lat+lon to also get local circumstances (type seen, magnitude, obscuration, contact times C1-C4). Lunar eclipses report type and magnitude; add lat+lon to learn whether the Moon is above the horizon there. Times to the second vs Swiss Ephemeris (stations to ~1 min: ill-conditioned by nature). Range <= 370 days.
Parameters (8)
startstringrequired
UTC ISO start date (convert from local first)
endstringrequired
UTC ISO end date; range <= 370 days
kindsarrayrequired
Event kinds to include
bodystring
Required for rise/set/transit/station/crossing
latnumber
Required for rise/set/transit
lonnumber
Required for rise/set/transit
target_lonnumber
Zodiac longitude for 'crossing', degrees
zodiacstring
Zodiac for 'crossing' longitudes
planetary_hours
Planetary hours for a moment and place: the unequal hour in effect (its ruler, day/night, hour number 1-24, start/end UTC), the ruler of the planetary day, and the full 24-hour ruler sequence. Hours split the day (sunrise to sunset) and night (sunset to next sunrise) into twelve each; the day ruler is the weekday ruler and the hours follow the Chaldean order. Needs lat+lon. Returns available:false above the polar circles when the Sun does not rise or set that day.
Parameters (3)
datestring
UTC ISO date-time (convert from local first); omit for now
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
void_of_course
Void-of-course Moon at a moment: whether the Moon makes no further Ptolemaic aspect to a traditional planet (Sun..Saturn) before it leaves its current sign. Returns the Moon's sign, the UTC time it exits that sign, and the UTC time of its next perfecting aspect (null when none remains -- i.e. void). Tropical by default.
Parameters (2)
datestring
UTC ISO date-time (convert from local first); omit for now
zodiacstring
tropical (default) or sidereal:<ayanamsa>
returns
Solar or lunar return: the instant(s) a body returns to its natal longitude within a window, plus the full return chart for the first one. The Sun returns about yearly (the solar-return chart for the year), the Moon about monthly. Return chart is cast for the return moment at return_lat/return_lon (defaults to the birthplace; pass the current/relocated place for a relocated return).
Parameters (10)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
bodystringrequired
sun for the solar return, moon for the lunar return
search_startstringrequired
UTC ISO start of the window to search for returns
search_endstringrequired
UTC ISO end of the window; range <= 2 years
return_latany
Latitude for the return chart; defaults to the birth latitude
return_lonany
Longitude (EAST positive) for the return chart; defaults to the birth longitude
house_systemstring
House system (default placidus). Case- and spacing-insensitive; valid: placidus, whole_sign, equal, porphyry, koch, regiomontanus, campanus, alcabitius, morinus, meridian, polich_page, vehlow (aliases like "whole sign" also work).
zodiacstring
tropical (default) or sidereal:<ayanamsa>
progressions
Secondary progressions (day-for-a-year) and solar-arc directions of a natal chart to a target date. Returns, per body, the secondary-progressed longitude and the solar-arc-directed longitude, plus the solar arc itself. Longitudes only (no houses), so no birthplace is needed.
Parameters (3)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
target_datestringrequired
UTC ISO date to progress/direct to (convert from local first)
zodiacstring
tropical (default) or sidereal:<ayanamsa>
composite
Relationship charts for two people: the midpoint composite (each body and angle is the shorter-arc midpoint of the two natal positions) and the Davison chart (a real chart cast for the midpoint in time and place). Each person needs date+lat+lon.
Parameters (4)
aobjectrequired
Person A birth data (UTC date, lat, lon)
bobjectrequired
Person B birth data (UTC date, lat, lon)
house_systemstring
House system (default placidus). Case- and spacing-insensitive; valid: placidus, whole_sign, equal, porphyry, koch, regiomontanus, campanus, alcabitius, morinus, meridian, polich_page, vehlow (aliases like "whole sign" also work).
zodiacstring
tropical (default) or sidereal:<ayanamsa>
dignities
Essential dignity and sect for the seven traditional planets at a moment and place. Per planet: its sign, any essential dignity (domicile/exaltation/detriment/fall), its weighted essential-dignity score (Lilly: rulership 5, exaltation 4, triplicity 3, term 2, face 1; detriment -5, fall -4) with a peregrine flag, its planetary sect (diurnal/nocturnal, null for Mercury), and whether it is in sect given a day or night chart. The chart is day when the Sun is above the horizon — so lat+lon are required.
Parameters (4)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
zodiacstring
tropical (default) or sidereal:<ayanamsa>
lots
The seven Hermetic lots (Arabic parts) — Fortune, Spirit, Eros, Necessity, Courage, Victory, Nemesis — cast from the Ascendant and reversing direction by sect (a chart is day when the Sun is above the horizon). Per lot: its longitude and zodiacal position. Lots are anchored to the Ascendant, so an exact time and lat+lon are required. Fortune and Spirit are mirror images about the Ascendant. Tropical by default.
Parameters (4)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
zodiacstring
tropical (default) or sidereal:<ayanamsa>
profections
Annual and monthly profections (a Hellenistic time-lord technique) at a target date. The natal Ascendant advances one whole sign per year of life; the profected sign's traditional ruler is the lord of the year, the single most important time-lord for that year. Returns the age in years, the month within the profection year, and the annual and monthly profected sign (with its whole-sign house from the natal Ascendant and its lord). Needs the birth time and place for the Ascendant.
Parameters (5)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
target_datestringrequired
UTC ISO date to profect to (convert from local first)
zodiacstring
tropical (default) or sidereal:<ayanamsa>
firdaria
Firdaria (firdariyyat): the Persian/medieval planetary time-lord periods. Life divides into nine major periods totalling 75 years — the seven planets (a day chart starts with the Sun, a night chart with the Moon) then the North and South Nodes — each planetary period split into seven sub-periods. Returns the full timeline (each period and sub-period with UTC start/end) and, when target_date is given, the major and sub lord active then. Sect is taken from the birth chart, so lat+lon are required; pure time arithmetic, no zodiac.
Parameters (4)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
target_datestring
UTC ISO date to look up the active period for; omit for the timeline only
releasing
Zodiacal releasing (aphesis), the Hellenistic time-lord technique from Vettius Valens, released from a Lot (Spirit by default, or Fortune). From the Lot's sign, periods release sign by sign with planetary minor-year lengths on the 360-day-year convention; each level is a twelfth of the one above (L1..L4), and a loop back to the starting sign looses the bond, jumping once to the opposite sign (+6). Returns the timeline down to max_level over the horizon and, when target_date is given, the L1..L4 lords active then. Anchored to the natal Lot, so an exact time and lat+lon are required.
Parameters (8)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
target_datestring
UTC ISO date to read the active L1..L4 periods for; omit for the timeline only
lotstring
the Lot to release from (default spirit)
max_levelinteger
deepest sub-period level in the timeline, 1..4 (default 2)
horizon_yearsnumber
timeline length in 360-day years from birth (default 100)
zodiacstring
tropical (default) or sidereal:<ayanamsa>
directions
Primary (mundane) directions of the seven traditional planets to the four angles (MC, IC, Ascendant, Descendant), and optionally between the planets themselves. The diurnal rotation carries a body to the angle (or a promissor to a significator); the arc of rotation, converted by a time key (Naibod 0.9856473°/yr by default, or Ptolemy 1°/yr), gives the age of the direction. Returns the directions within max_years, sorted by age, each with its arc, age in years, and UTC date. With include_mundane, also returns the planet-to-planet (promissor → significator) directions. Circumpolar bodies have no Ascendant/Descendant directions. Needs the birth time and place; equatorial, so zodiac is irrelevant.
Parameters (6)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
keystring
time key: naibod (0.9856473°/yr, default) or ptolemy (1°/yr)
max_yearsnumber
only directions reached within this many years of life (default 90)
include_mundaneboolean
also return inter-planetary (promissor → significator) directions (default false)
nakshatras
The nakshatra (one of the 27 lunar mansions of 13°20′) of each classical point on the sidereal zodiac: the seven traditional planets and the Ascendant (lagna). Per point: the nakshatra name, its pada (quarter, 1–4), the ruling planet (the Vimshottari lord), and degrees into the nakshatra. The Moon's nakshatra (janma nakshatra) anchors the Vimshottari dasha. Sidereal by definition; Lahiri ayanamsa by default. Needs the birth time and place for the Ascendant.
Parameters (4)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
zodiacstring
sidereal ayanamsa (default sidereal:lahiri); these are sidereal techniques
dasha
Vedic dasha periods — planetary time-lord cycles started from the Moon's birth nakshatra. system selects Vimshottari (120-year, the standard), Yogini (36-year, eight yoginis), or Ashtottari (108-year). Returns the period timeline (mahadasha → antardasha) with UTC start/end, the balance of the first period at birth, and — when target_date is given — the lords active then (Vimshottari also gives the pratyantardasha). Sidereal; Lahiri by default. Needs the birth time and place.
Parameters (7)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
systemstring
dasha system: vimshottari (120y), yogini (36y), or ashtottari (108y)
target_datestring
UTC ISO date to read the active lords for; omit for the timeline only
levelsinteger
deepest timeline level: 1 (maha) or 2 (maha+antar, default)
zodiacstring
sidereal ayanamsa (default sidereal:lahiri); these are sidereal techniques
vargas
Parashari divisional charts (vargas): the sign of each of the seven planets and the Ascendant in the requested D-charts — D1 rasi, D2 hora, D3 drekkana, D9 navamsa, D10 dasamsa, D12 dwadasamsa, D30 trimsamsa. Per point in each chart: the divisional sign and the division number within the rasi. The navamsa (D9) is the most consulted after the rasi. Sidereal; Lahiri by default. Needs the birth time and place for the Ascendant.
Parameters (5)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
divisionsarray
subset of 1/2/3/9/10/12/30 (default all)
zodiacstring
sidereal ayanamsa (default sidereal:lahiri); these are sidereal techniques
yogas
Vedic yogas (planetary combinations) on the sidereal rasi chart: the five Pancha Mahapurusha yogas (Ruchaka, Bhadra, Hamsa, Malavya, Shasha), Gajakesari, Budha-Aditya, and Chandra-Mangala; whether Kemadruma (the isolated-Moon yoga) is present; the raja yogas (a kendra lord associating with a trikona lord) and dhana (wealth) yogas, each as the lord pair and how they associate (conjunction, aspect, or exchange); and the chart's yogakarakas (a planet ruling both a kendra and a trikona). Sidereal; Lahiri by default. Needs the birth time and place.
Parameters (4)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
zodiacstring
sidereal ayanamsa (default sidereal:lahiri); these are sidereal techniques
aspect_patterns
Classical aspect configurations in a chart: T-squares, grand trines, grand crosses, yods, kites, mystic rectangles, and stelliums by sign and by house. Each is a structured object with the participating bodies and the worst defining-aspect orb; T-squares and yods also name the apex, stelliums their sign or house. Reported patterns are maximal — a grand cross hides the T-squares it contains, a kite its grand trine. Pure geometry (engine orbs plus a quincunx for yods), no interpretation. Needs date, lat, lon.
Parameters (5)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
house_systemstring
House system (default placidus). Case- and spacing-insensitive; valid: placidus, whole_sign, equal, porphyry, koch, regiomontanus, campanus, alcabitius, morinus, meridian, polich_page, vehlow (aliases like "whole sign" also work).
zodiacstring
tropical (default) or sidereal:<ayanamsa>
chart_signature
A chart's structural signature as plain counts: element, modality, angularity, quadrant, and hemisphere distributions over the bodies; the dominant element, modality, and most-occupied sign; and the classical chart ruler (the ruler of the Ascendant's sign). Counts only, no interpretation — a compact summary for emphasis and comparison. Needs date, lat, lon.
Parameters (5)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
house_systemstring
House system (default placidus). Case- and spacing-insensitive; valid: placidus, whole_sign, equal, porphyry, koch, regiomontanus, campanus, alcabitius, morinus, meridian, polich_page, vehlow (aliases like "whole sign" also work).
zodiacstring
tropical (default) or sidereal:<ayanamsa>
chart_facts
A chart's validated facts as ranked, citable atoms for interpretation. Each fact has a stable id (e.g. "aspect:moon~neptune:conjunction"), the bodies it concerns, a salience score (luminaries, angular placements, the chart ruler, tight/hard aspects, configurations rank high), and a plain-language statement. Facts span placements, aspects, configurations, the structural signature, dispositors and receptions, a body's tight conjunction with a bright fixed star (e.g. "star:jupiter:Sirius"), and the Part of Fortune and Spirit (e.g. "lot:fortune"). Read the facts, write the interpretation in your own words, and cite the [id] each statement rests on — do not introduce facts not listed. Returns the ranked facts plus a ready-to-interpret `brief`.
By default a real birth chart: pass date+lat+lon. The chart's grounding is first-class via `realm` (what it is: observed/forecast/fictional/mythic/archetypal/…) and the time: an exact `date`, an uncertain `earliest`+`latest` range (the brief then frames it as provisional and trusts the Moon/angles/houses less), `constraints` for an archetypal chart with no time (synthesized via the compiler), or a full structured `when` (relative-to-another-event or a narrative calendar). A `when` of kind `relative` looks its `anchorId` up in `anchors` (a map of id → UTC instant supplied in the request). Omit lat+lon for a placeless chart (nominal houses).
Parameters (14)
datestring
Exact UTC instant, ISO 8601 (e.g. 1990-06-10T14:30:00Z); convert local to UTC first
earlieststring
Start of an uncertain-time range (UTC ISO); use with `latest` instead of `date`
lateststring
End of an uncertain-time range (UTC ISO)
whenany
Full structured temporal anchor; overrides date/earliest/latest. Use for relative or narrative time.
anchorsobject
Reference instants for a `relative` when: { anchorId: UTC ISO }
latnumber
Latitude, north positive
lonnumber
Longitude, EAST positive (Americas are negative)
realmstring
What the chart is; frames the interpretation (default observed)
constraintsarray
Geometric constraints for an archetypal/conceptual chart with no time (compiler synthesis)
house_systemstring
House system (default placidus). Case- and spacing-insensitive; valid: placidus, whole_sign, equal, porphyry, koch, regiomontanus, campanus, alcabitius, morinus, meridian, polich_page, vehlow (aliases like "whole sign" also work).
zodiacstring
tropical (default) or sidereal:<ayanamsa>
target_datestring
UTC ISO instant for transits and time-lords vs this natal chart; omit for natal-only facts
include_vedicboolean
With target_date: project nakshatra/varga/yoga (default true when zodiac is sidereal)
limitinteger
max facts to return, highest salience first (default 24)
counterfactual_chart
A birth chart, perturbed — a 'what if'. Give a base chart (date+lat+lon) and an edit: `shift_time` (e.g. '1h', '-30m', 'P1D') moves the instant ("born an hour later"), `move_lat`+`move_lon` recompute at another place, and/or `set_longitudes` moves bodies to new ecliptic degrees ("Mars in the next sign"). Returns the diff vs the original: bodies that changed sign or house, aspects gained or lost, and angles that changed sign. A time/place edit rotates the houses and angles while planets stay put; a longitude splice moves only those bodies and recomputes their aspects.
Parameters (9)
datestringrequired
UTC date-time, ISO 8601, e.g. 1990-06-10T14:30:00Z. Convert local birth time to UTC first.
latnumberrequired
Latitude, north positive
lonnumberrequired
Longitude, EAST positive (Americas are negative)
shift_timestring
Duration to shift the instant: '1h', '-30m', 'P1Y'
move_latany
Recompute at this latitude instead of the birth latitude
move_lonany
Recompute at this longitude instead of the birth longitude
set_longitudesobject
Move bodies to these ecliptic longitudes in degrees, e.g. { "mars": 45 }
house_systemstring
House system (default placidus). Case- and spacing-insensitive; valid: placidus, whole_sign, equal, porphyry, koch, regiomontanus, campanus, alcabitius, morinus, meridian, polich_page, vehlow (aliases like "whole sign" also work).
zodiacstring
tropical (default) or sidereal:<ayanamsa>
similar_skies
Find when the sky most resembled a reference moment. Builds a feature vector for the reference date's planetary configuration and scans a window for the closest matches by cosine similarity (1.0 = identical configuration). Answers 'when did the sky last look like this?' for transit echoes and historical analogues. Returns the top matches with their similarity, highest first.
Parameters (5)
reference_datestringrequired
UTC ISO date whose sky is the target to match
startstringrequired
UTC ISO start of the search window
endstringrequired
UTC ISO end of the search window
step_daysnumber
sampling step in days (default 1)
limitinteger
max matches to return (default 10)
electional_search
Rank moments in a window for an electional aim. Samples the window and scores each instant by how closely a set of wanted body-to-body aspects is satisfied (tighter and applying aspects score higher), optionally penalizing a void-of-course Moon. Returns the top moments with the aspects that matched. Body-to-body only; for aspects to the angles, compute the chart at a candidate moment.
Parameters (7)
startstringrequired
UTC ISO start of the window
endstringrequired
UTC ISO end of the window
wantedarrayrequired
aspects to reward when close to exact
step_hoursnumber
sampling step in hours (default 6)
avoid_void_moonboolean
penalize a void-of-course Moon
limitinteger
max moments to return (default 10)
zodiacstring
tropical (default) or sidereal:<ayanamsa>
cosmic_weather
The mundane sky on a date: the active aspect configurations among the transiting planets (T-squares, grand trines, grand crosses, yods, kites, mystic rectangles, stelliums by sign), any planet stationing within a window, and whether the Moon is void of course. A 'cosmic weather' snapshot; no birth chart or location needed.
Clean-room astrology computation monorepo. MIT, no Swiss Ephemeris code, no
AGPL, no ephemeris files. Caelus computes ephemeris positions, charts, events,
hellenistic timing techniques, Vedic methods, citable chart facts, sky-view
image-prompt frames, and the MCP tools around them. Live at
ephemengine.com.
The Python reference engine and data-fitting pipeline live in python/;
they mint the coefficient data and golden fixtures and are not a runtime
dependency.
