---
title: "Render a deterministic natal/transit double wheel"
method: POST
path: "/api/astro/transit-svg"
tags: ["Calculations"]
---

# Render a deterministic natal/transit double wheel

`POST /api/astro/transit-svg`

## Request

- Base URL: `https://api.cosmicephemeris.com`
- URL: `https://api.cosmicephemeris.com/api/astro/transit-svg`
- Auth: one of:
  - HTTP bearer
  - API key in header `x-api-key`

Returns an original 1200 by 1120 SVG in JSON. Natal houses are inside; requested transit positions are outside. Opt-in include_png returns a deterministic metadata-free PNG derived from the same internal SVG; omission or false preserves the predecessor response exactly. No uploaded markup, image, font or URL is accepted. failed or timed-out admitted attempts are not refunded.
Historical mode uses an explicit BCE/CE date object and UT1 conventions. Its response is the versioned historical envelope, not the modern UTC envelope. Read result for calculation fields and metadata for limits and uncertainty.

## Request body

- union
  - TransitSvgRequest
    - `zodiac` string, nullable: tropical or sidereal; server trims whitespace and ignores case. Omitted/null selects tropical.
    - `ayanamsa` string, nullable: Sidereal supports lahiri, raman, krishnamurti, fagan_bradley, yukteshwar, sassanian, true_chitra, true_revati, true_pushya, galactic_center_0_sagittarius, galactic_alignment_mardyks, with case/whitespace normalization; other names return 400 in sidereal mode. Omitted/null selects lahiri. Tropical mode ignores a nonempty string and outputs null. This schema describes that compatibility behavior rather than claiming every string is a supported sidereal model.
    - `house_system` 'equal' | 'whole_sign' | 'placidus'
    - `theme` 'light' | 'dark' | 'monochrome'
    - `show_aspects` boolean
    - `include_png` boolean: When true, also returns a deterministic PNG derived only from this response's server-rendered SVG. Omission or false preserves the predecessor response exactly.
    - `birth` CalculationBirthInput, required: Strict nested birth input; no unknown properties, nulls, booleans or numeric strings. Known civil time required; semantic date/DST/undefined-angle validation occurs on the server.
      - `date` string, date, required: Valid Gregorian YYYY-MM-DD local civil date, inclusive 1800-01-01 through 2200-12-31. Calendar validity and timezone conversion are checked by the server.
      - `time` string, required: HH:MM or HH:MM:SS; no offset in this field. Use timezone to select the civil-time zone.
      - `timezone` string: Valid IANA zone; UTC when omitted. Ambiguous and nonexistent civil times are rejected.
      - `lat` number, required
      - `lon` number, required
    - `transitDate` string, date, required: Valid Gregorian YYYY-MM-DD local civil date, inclusive 1800-01-01 through 2200-12-31. Calendar validity and timezone conversion are checked by the server.
    - `transitTime` string: HH:MM or HH:MM:SS; no offset in this field. Use timezone to select the civil-time zone.
    - `timezone` string, nullable: IANA timezone name (for example America/New_York). Omission, null, or empty string means UTC for a birth input. Nonexistent or ambiguous local clock-change times return 400; provide the known UTC date/time with timezone UTC instead.
  - HistoricalTransitSvgRequest: Explicit historical mode, 1000 BCE (BC)–2500 CE (AD). No year zero, implicit calendar, UTC or IANA zone. Preserve tool-specific mathematical, geographic and search limits; calendar/time conventions and estimated Delta-T are not certified historical accuracy.
    - `zodiac` string, nullable: tropical or sidereal; server trims whitespace and ignores case. Omitted/null selects tropical.
    - `ayanamsa` string, nullable: Sidereal supports lahiri, raman, krishnamurti, fagan_bradley, yukteshwar, sassanian, true_chitra, true_revati, true_pushya, galactic_center_0_sagittarius, galactic_alignment_mardyks, with case/whitespace normalization; other names return 400 in sidereal mode. Omitted/null selects lahiri. Tropical mode ignores a nonempty string and outputs null. This schema describes that compatibility behavior rather than claiming every string is a supported sidereal model.
    - `house_system` 'equal' | 'whole_sign' | 'placidus'
    - `theme` 'light' | 'dark' | 'monochrome'
    - `show_aspects` boolean
    - `include_png` boolean: When true, also returns a deterministic PNG derived only from this response's server-rendered SVG. Omission or false preserves the predecessor response exactly.
    - `birth` object, required: Strict nested birth input; no unknown properties, nulls, booleans or numeric strings. Known civil time required; semantic date/DST/undefined-angle validation occurs on the server.
      - `date` HistoricalDate, required: Explicit civil date, 1000 BCE (BC)–2500 CE (AD); no year zero. Calendar validity is checked by the server. Available only on documented connected historical operations, with explicit UT1/fixed-offset conventions.
        - `year` integer, required
        - `era` 'BCE' | 'CE', required: Display BCE (BC) / CE (AD); API values remain BCE / CE. No year zero.
        - `month` integer, required
        - `day` integer, required
        - `calendar` 'proleptic_gregorian' | 'proleptic_julian', required: Explicit choice; applies the selected calendar rules throughout history without a regional adoption switch.
      - `time` string, required: HH:MM or HH:MM:SS; no offset in this field. Use timezone to select the civil-time zone.
      - `timezone` string, required: Explicit UT1 or fixed offset UT1+/-HH:MM[:SS], within 14 hours. Local clock minus offset yields UT1, not UTC. No IANA timezone inference. Original offset spelling is preserved.
      - `lat` number, required
      - `lon` number, required
    - `at` HistoricalDateTime, required: Shared historical input contract; parsing alone does not enable a calculation route. Derived calculation records can include fractional seconds and are not this input type.
      - `date` HistoricalDate, required: Explicit civil date, 1000 BCE (BC)–2500 CE (AD); no year zero. Calendar validity is checked by the server. Available only on documented connected historical operations, with explicit UT1/fixed-offset conventions.
        - `year` integer, required
        - `era` 'BCE' | 'CE', required: Display BCE (BC) / CE (AD); API values remain BCE / CE. No year zero.
        - `month` integer, required
        - `day` integer, required
        - `calendar` 'proleptic_gregorian' | 'proleptic_julian', required: Explicit choice; applies the selected calendar rules throughout history without a regional adoption switch.
      - `time` string, required: Explicit HH:MM[:SS]; whole seconds only, no leap seconds. Normalized helper output includes seconds.
      - `timezone` string, required: Explicit UT1 or fixed offset UT1+/-HH:MM[:SS], within 14 hours. Local clock minus offset yields UT1, not UTC. No IANA timezone inference. Original offset spelling is preserved.

## Response `200`

JSON-wrapped SVG.

- union
  - RelationshipSvgResponse
    - `type` 'synastry_svg' | 'transit_svg', required
    - `status` 'current', required
    - `svg` string, required
    - `metadata` object, required
    - `png` PngExport: Deterministic, metadata-free PNG rendered from Cosmic Ephemeris's own SVG primitive subset. No uploaded SVG, URL, font, browser, or external rendering service is accepted.
      - `media_type` 'image/png', required
      - `base64` string, required: Base64-encoded PNG bytes; decode as an image, never HTML.
      - `bytes` integer, required
      - `sha256` string, required
      - `width` 1200, required
      - `height` 800 | 1100 | 1120 | 1420, required
      - `renderer` 'cosmicephemeris-original-png-v1', required
      - `source_svg_sha256` string, required
  - HistoricalTransitSvgRelationshipSvgResponse
    - `schema` 'cosmicephemeris-historical-calculation-v1', required
    - `status` 'historical', required
    - `type` 'transit-svg', required
    - `input` HistoricalTransitSvgRequest, required: Explicit historical mode, 1000 BCE (BC)–2500 CE (AD). No year zero, implicit calendar, UTC or IANA zone. Preserve tool-specific mathematical, geographic and search limits; calendar/time conventions and estimated Delta-T are not certified historical accuracy.
      - `zodiac` string, nullable: tropical or sidereal; server trims whitespace and ignores case. Omitted/null selects tropical.
      - `ayanamsa` string, nullable: Sidereal supports lahiri, raman, krishnamurti, fagan_bradley, yukteshwar, sassanian, true_chitra, true_revati, true_pushya, galactic_center_0_sagittarius, galactic_alignment_mardyks, with case/whitespace normalization; other names return 400 in sidereal mode. Omitted/null selects lahiri. Tropical mode ignores a nonempty string and outputs null. This schema describes that compatibility behavior rather than claiming every string is a supported sidereal model.
      - `house_system` 'equal' | 'whole_sign' | 'placidus'
      - `theme` 'light' | 'dark' | 'monochrome'
      - `show_aspects` boolean
      - `include_png` boolean: When true, also returns a deterministic PNG derived only from this response's server-rendered SVG. Omission or false preserves the predecessor response exactly.
      - `birth` object, required: Strict nested birth input; no unknown properties, nulls, booleans or numeric strings. Known civil time required; semantic date/DST/undefined-angle validation occurs on the server.
        - `date` HistoricalDate, required: Explicit civil date, 1000 BCE (BC)–2500 CE (AD); no year zero. Calendar validity is checked by the server. Available only on documented connected historical operations, with explicit UT1/fixed-offset conventions.
          - `year` integer, required
          - `era` 'BCE' | 'CE', required: Display BCE (BC) / CE (AD); API values remain BCE / CE. No year zero.
          - `month` integer, required
          - `day` integer, required
          - `calendar` 'proleptic_gregorian' | 'proleptic_julian', required: Explicit choice; applies the selected calendar rules throughout history without a regional adoption switch.
        - `time` string, required: HH:MM or HH:MM:SS; no offset in this field. Use timezone to select the civil-time zone.
        - `timezone` string, required: Explicit UT1 or fixed offset UT1+/-HH:MM[:SS], within 14 hours. Local clock minus offset yields UT1, not UTC. No IANA timezone inference. Original offset spelling is preserved.
        - `lat` number, required
        - `lon` number, required
      - `at` HistoricalDateTime, required: Shared historical input contract; parsing alone does not enable a calculation route. Derived calculation records can include fractional seconds and are not this input type.
        - `date` HistoricalDate, required: Explicit civil date, 1000 BCE (BC)–2500 CE (AD); no year zero. Calendar validity is checked by the server. Available only on documented connected historical operations, with explicit UT1/fixed-offset conventions.
          - `year` integer, required
          - `era` 'BCE' | 'CE', required: Display BCE (BC) / CE (AD); API values remain BCE / CE. No year zero.
          - `month` integer, required
          - `day` integer, required
          - `calendar` 'proleptic_gregorian' | 'proleptic_julian', required: Explicit choice; applies the selected calendar rules throughout history without a regional adoption switch.
        - `time` string, required: Explicit HH:MM[:SS]; whole seconds only, no leap seconds. Normalized helper output includes seconds.
        - `timezone` string, required: Explicit UT1 or fixed offset UT1+/-HH:MM[:SS], within 14 hours. Local clock minus offset yields UT1, not UTC. No IANA timezone inference. Original offset spelling is preserved.
    - `result` object, required: Complete historical calculation adapter result. Times are explicit UT1 date records, never UTC strings; derived times may include fractional seconds and years outside the input range.
    - `metadata` object, required
      - `time_standard` 'UT1', required
      - `historical_accuracy_certified` unknown, required
      - `warnings` string[], required

## Other responses

- `400`: Invalid request, malformed JSON, out-of-range date/location, unknown model, invalid timezone or ambiguous/nonexistent clock-change time. Invalid attempts reaching quota reservation consume one unit.
- `401`: Missing, invalid, revoked API key or unavailable activated key owner. Dashboard cookies do not authenticate calculation routes.
- `403`: Origin not allowed by production CORS policy. Server-to-server requests can omit Origin.
- `429`: Monthly quota exhausted, per-user two-request concurrency reached, or nginx rate/connection admission refused. Retry-After: 2 is sent for application per-user concurrency only, not a promise that monthly quota resets in two seconds.
- `502`: Engine unavailable, unsuccessful internal server response or invalid upstream JSON. No engine internals are exposed.
- `503`: Four-request global calculation pool full (Retry-After: 2), maintenance or upstream service unavailable.
- `504`: Application engine timeout: 15 seconds normally; planetary events, house ingresses, aspect windows, event calendar, eclipse geometry, electional search, and event-rule search use 30 seconds; Nakshatra Timeline plus the explicitly enumerated readiness, robustness, location, uncertainty, and electional-audit family use 60 seconds. Timer includes response-body parsing; an admitted timeout consumes quota.

---

[API](https://skmtc.dev/cosmicephemeris/apis/cosmic-ephemeris-calculation-api.md) · [All operations](https://skmtc.dev/cosmicephemeris/apis/cosmic-ephemeris-calculation-api/llms.txt) · [OpenAPI document](https://skmtc.dev/cosmicephemeris/apis/cosmic-ephemeris-calculation-api/revisions/f041e924cea3?raw)