---
title: "Get Eclipse Elements"
method: GET
path: "/eclipse/elements/{eclipse_date}"
tags: ["eclipse"]
---

# Get Eclipse Elements

`GET /eclipse/elements/{eclipse_date}`

The raw Besselian elements + conventions for a central eclipse.

Powers the client-side umbra engine (the web app ports the ring geometry to
TypeScript): it evaluates these polynomials in the browser to draw the shadow
without a round-trip per frame, reproducing the server's rings. 404s with the
available dates for an unknown eclipse.

## Path parameters

- `eclipse_date` string, required

## Response `200`

Successful Response

- BesselianElementsResponse — The raw Besselian element set for one central eclipse, plus the exact conventions needed to evaluate it client-side. This is the ground truth the server's own solver runs on — a client that ports the geometry reproduces the server's rings to the metre.
  - `eclipse_date` string, required
  - `eclipse_type` string, required — total / annular / hybrid
  - `t0_tdt_hours` number, required — Reference epoch t0, decimal hours TDT
  - `delta_t_seconds` number, required — TDT − UT at the eclipse (seconds)
  - `jd_tdt` number, nullable — Julian Date (TDT) of the reference epoch
  - `tan_f1` number, required — Penumbral cone half-angle tangent
  - `tan_f2` number, required — Umbral cone half-angle tangent
  - `x` number[], required
  - `y` number[], required
  - `d` number[], required
  - `l1` number[], required
  - `l2` number[], required
  - `mu` number[], required
  - `greatest_eclipse` GreatestEclipseOut
    - `ut` string, required — Instant of greatest eclipse (UT, HH:MM:SS.s)
    - `lat` number, required
    - `lon` number, required
  - `conventions` ElementConventions — How to consume the raw Besselian polynomials — enough for a client to reproduce the Python umbra rings exactly (the web app ports ``_umbra_edge_ring`` / ``_project_to_ground`` to TypeScript).
    - `polynomials` string
    - `time_variable` string
    - `length_units` string
    - `angle_units` string
    - `delta_t` string
    - `hour_angle` string
    - `earth_rotation_deg_per_s` number — omega: Earth's sidereal rotation rate used in the H term.
    - `ellipsoid_flattening_ratio` number — b/a (= sqrt(1−e²)) for the reference ellipsoid; used to reduce geographic latitude to geocentric (rho·sin φ' / rho·cos φ').
    - `earth_equatorial_radius_km` number
    - `coordinates` string
  - `attribution` string

## Other responses

- `422` — Validation Error

---

[API](https://skmtc.dev/stardrift/apis/fastapi.md) · [All operations](https://skmtc.dev/stardrift/apis/fastapi/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/stardrift/fastapi/revisions/00746572572a/schema)