This simulator is MIT licensed — Copyright (c) 2026 Christopher W Ingram. Everything below came from somewhere else, and is listed with the terms it carries. Nothing listed here restricts redistribution.
Peter Duffett-Smith, 3rd edition, Cambridge University Press, 1988.
What is used: the methods. Not the text, and not the code listings.
The astronomical routines are implemented from the published algorithms. Copyright protects expression, not mathematical procedures, so an independent implementation of a published method is not a derivative of the book. Three things were done deliberately to keep that boundary clean:
One item to be aware of. The lunar routine carries six elements at the 1990 January 0.0 epoch — mean longitude, longitude of perigee, longitude of the node, inclination and eccentricity — marked in the code as taken from the book. These are astronomical measurements, i.e. facts, and facts attract no copyright; they also appear in many independent sources, being derived from standard ephemerides.
The solar routine does not have this question hanging over it: it uses the book's method with J2000-referred elements taken from the general literature rather than the book's epoch values.
Source: NASA GSFC eclipse site, from the Five Millennium Canon of Solar
Eclipses — one element set for each of the 34 solar eclipses in
this catalogue.
eclipse.gsfc.nasa.gov
Work of the US Government, in the public domain, and individual element
sets are facts in any case. Acknowledgement is customary and is carried in
each data file's own provenance block, which records the page
it came from, the date it was taken, the ephemeris used
(VSOP87 / ELP2000-82), the adopted ΔT, and the fact that the elements
refer to the Moon's centre of mass with no limb profile.
The later SEbeselm pages (VSOP87 / ELP2000-85) give a
ΔT about 4.3 s lower and state a validity window; that ΔT is
stored alongside as a selectable alternative and the window is adopted. The
two are shown side by side and neither is edited toward the other.
The elements are stored exactly as published and are never edited.
Source: NASA GSFC five millennium canon of lunar eclipses — the 35
lunar eclipses in this catalogue.
eclipse.gsfc.nasa.gov — lunar eclipses
Work of the US Government, in the public domain; individual contact times are facts and are not copyrightable in any case.
These times are the authority and are never computed from this project's own Moon, which could not derive them to useful accuracy: the Earth's umbra at the Moon's distance is about 0.75° across, while the Moon of the low-precision routines is roughly 0.1° out — some eleven minutes of contact time.
NASA publishes no machine-readable per-eclipse contact times for lunar eclipses, so for all but one event the contacts are derived from the published catalogue as greatest eclipse plus and minus half of each published phase duration — arithmetic on published values, not a recomputation. Checked against 28 August 2026, whose contacts were taken from published contact times directly, the derivation agrees to within 3 seconds. Every file records which of the two it carries, and a file that cannot say where its numbers came from is refused.
The ΔT model in this project implements the polynomial expressions of
Espenak & Meeus, published by NASA alongside the
Five Millennium Canon of Solar Eclipses and derived in part from
Morrison & Stephenson (2004).
eclipse.gsfc.nasa.gov — Polynomial Expressions for
ΔT
Several other standard series follow the forms given in Meeus, Astronomical Algorithms (2nd edition, Willmann-Bell, 1998): the low-precision nutation in longitude and obliquity, the mean obliquity of the ecliptic, the solar equation of centre, and the IAU 1976 precession angles. As with Duffett-Smith, what is used is the method and the published constants, independently implemented — no text and no code listings are reproduced.
A note in fairness to those expressions. Every future eclipse here uses the Espenak–Meeus prediction, because nothing else is available for a date that has not happened. Where a measurement exists it is preferred: 12 August 2026 uses the measured IERS value, which is 6.2 s smaller than the prediction NASA adopted for it. That is not a fault in the expressions. They exist to supply ΔT where no measurement is possible, and they held to about six seconds over a span of years. The page always says which kind it is using, and never presents a prediction as a measurement.
Source: Natural Earth 1:110m physical coastline, via the natural-earth-vector
repository.
naturalearthdata.com — terms of use
Released into the public domain. No permission required and no attribution required, though Natural Earth ask to be credited where practical, which this page does. The geometry is unmodified apart from coordinate rounding, which the generated file records in its own provenance block.
Source: Natural Earth 1:10m populated places, via the natural-earth-vector
repository — the gazetteer behind the site list.
naturalearthdata.com — terms of use
Released into the public domain, with the same request to be credited where practical. A subset is used: every national capital plus the most populous remaining places, at most two non-capitals per country so that no one country crowds out the rest. Name, country, coordinates and IANA time zone are carried unmodified apart from coordinate rounding.
Where a place carries no time zone in the source — Tripoli, Sanaa, Moscow and Sydney among them — the zone of the nearest place in the same country is used instead, and the entry records which place it came from. That is an inference, not source data, and is marked as such.
Used as test expectations only — a small number of individual published values, each cited at the point of use. Individual facts are not subject to copyright, and this is nowhere near a substantial extraction from any database.
A planned high-precision tier would add truncated VSOP87 (Bretagnon & Francou) and ELP2000-82B (Chapront-Touzé & Chapront) series. Both are published for scientific use and are widely redistributed, but the terms of whichever distribution the coefficients come from should be checked, and an entry added here, before they are included.