# Skyfold Local Eclipse Circumstances

> Solar and lunar eclipses 2020–2040 as seen from your place, with contact times. For a place, lists every solar and lunar eclipse from 2020 to 2040 with what you will see: partial, annular or total, contact times C1–C4, magnitude, obscuration, duration and the Sun or Moon altitude, computed from NASA Besselian elements.

Part of usefulweb.app (https://usefulweb.app/). Part of [Skyfold](https://skyfold.usefulweb.app/) (ownerApp: skyfold). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://skyfoldeclipselocal.usefulweb.app/ (interactive tool at https://skyfoldeclipselocal.usefulweb.app/tool)
- JSON API: POST https://skyfoldeclipselocal.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://skyfoldeclipselocal.usefulweb.app/api/v1/tool)
- OpenAPI: https://skyfoldeclipselocal.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://skyfoldeclipselocal.usefulweb.app/mcp - tool `skyfold_eclipse_local`

## Inputs
- location (text): Location (latitude, longitude) - Decimal degrees such as 52.09, 5.12 (north and east positive), or DMS, UTM, MGRS, Maidenhead or a plus code.
- elevation (number): Elevation above sea level
- timeZone (text): Time zone - IANA name such as Europe/Berlin or America/New_York, or a fixed offset such as UTC+2.
- fromYear (integer): From year
- toYear (integer): To year
- kind (select): Eclipses
- visibleOnly (boolean): Only eclipses visible from this place

## Method
- Solar eclipses: NASA/Espenak polynomial Besselian elements (VSOP87/ELP2000-85) with the classical local-circumstances iteration (Explanatory Supplement 1961; Meeus, Elements of Solar Eclipses): maximum where the shadow axis passes closest, contacts where the distance equals the penumbral (C1, C4) or umbral (C2, C3) radius.
- Magnitude = (L1 − m)/(L1 + L2); obscuration is the covered fraction of the solar disc area from circle overlap.
- Lunar eclipses: contact times from Espenak’s Five Millennium Catalog (greatest eclipse ± half the phase durations) and the Moon’s altitude from the Skyfold ephemeris.
- Times are converted from TD to UT with the ΔT used by NASA for each eclipse.

## Limits
- Contact times agree with NASA’s published city tables to within a minute; mountains, the lunar limb profile and local weather are not included. Never look at the Sun without certified eclipse glasses, except during totality.