Caelus
Caelus is a clean-room, MIT-licensed TypeScript suite for validated astrology computation. It computes planetary positions, charts, events, hellenistic timing techniques, Vedic methods, and citable chart facts across browser, edge, Node, and MCP clients, without Swiss Ephemeris code, AGPL licensing, or ephemeris files.
https://www.ephemengine.comOpens ChatGPT on the web or desktop and asks it to use the WebMCP tools available here.
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Last probed Sep 14, 2026 · www.ephemengine.com
35tools discovered
Showing 25 of 35 from the live probe.
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″, mea
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.
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 t
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 progr
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.
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.
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`.
Transits
Transiting planets vs natal chart: aspects within orb (applying/separating), natal house per transiting body.
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).
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).
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.
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 magn
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.
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.
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).
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.
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.
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 requir
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.
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.
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;
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
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,
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.
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.
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Directory coverage for brandsCaelus is a clean-room, MIT-licensed TypeScript suite for validated astrology computation. It computes planetary positions, charts, events, hellenistic timing techniques, Vedic methods, and citable chart facts across browser, edge, Node, and MCP clients, without Swiss Ephemeris code, AGPL licensing, or ephemeris files.
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MCPBundles probed 35 tools on the live server. The tool list on this page reflects what was discovered at the last refresh — connect your client to see the full set available to your session.
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