Computing Solar Eclipses — Research

Datasets

workingupdated 2026-09-15datasetsbesselianlolasldem2015srtmdeltatde440
  • NASA's machine-readable Besselian elements are one 5.95 MB CSV with 11,898 rows and 54 columns covering -1999 to +3000, including the cubic polynomial coefficients, tan⁡f1\tan f_1, tan⁡f2\tan f_2, t0t_0 and ΔT per eclipse.
  • SVS GIS products for 2017, 2023 and 2024 are zipped shapefiles and KML with central line, duration contours, obscuration contours, umbra polygons at 1-second and 10-second cadence, and a city-times JSON. The SVS host refused connections at the time of writing (2026 September), and the Wayback Machine served the pages.
  • Lunar topography: LOLA LDEM cylindrical grids at 4, 16, 64 and 128 pixels per degree as single IMG files of 2 MB to 2.1 GB, 256 pixels per degree in four hemisphere files, and 1024 pixels per degree in tiles of about 944 MB, plus SLDEM2015 in global and tiled forms. Kaguya (SELENE) LALT is at JAXA DARTS.
  • Terrestrial topography: SRTMGL1 (1 arcsecond) from LP DAAC and Copernicus GLO-30 from the AWS Open Data Registry.
  • ΔT: USNO deltat.data (observed) and deltat.preds (predicted), IERS finals.all.iau2000.txt for UT1-UTC and polar motion, and NASA's Canon polynomials for long-range values.
  • Ephemerides: JPL DE440 SPK (de440.bsp) and the NAIF lunar orientation kernel matching the ephemeris, moon_pa_de440_200625.bpc with frame kernel moon_de440_250416.tf for DE440, which is needed to orient a limb profile. tomasrojasc/eclipse-2026 pairs the older moon_pa_de421_1900-2050.bpc with DE421. The choice is argued in lunar figure, radius ratio k, and libration.

The question. For each dataset that the surveyed tools consume, what is the URL, the format and the version, and was it reachable?

Besselian element tables

NASA CSV. https://eclipse.gsfc.nasa.gov/eclipse_besselian_from_mysqldump2.csv, linked from the Five Millennium Catalog page as "Catalog of Solar Eclipse Besselian elements in CSV format" 1. Downloaded 2026-09-15: 5,952,576 bytes, 11,898 data rows plus header 2. Columns: year, month, day, td_ge, dt, luna_num, saros, eclipse_type, gamma, magnitude, lat_ge, lng_ge, lat_dd_ge, lng_dd_ge, sun_alt, sun_azm, path_width, central_duration, duration_secs, cat_no, canon_plate, julian_date, t0, x0, x1, x2, x3, y0, y1, y2, y3, d0, d1, d2, mu0, mu1, mu2, l10, l11, l12, l20, l21, l22, tan_f1, tan_f2, tmin, tmax, etype, PNS, UNS, NCN, nSer, nSeq, nJLE 2. The first row (-1999 June 12, type T) has dt = 46438.2 s, t0 = 3.0, x0 = -0.056331, x1 = 0.5538768, tan_f1 = 0.0046008, tan_f2 = 0.0045779, tmin = -3, tmax = 3 2. The dd and μ\mu polynomials are quadratic and xx and yy cubic in this file, matching the per-eclipse HTML pages 3. The elements were computed with VSOP87 and ELP-2000/82 and the Canon ΔT 1.

Per-eclipse HTML pages. https://eclipse.gsfc.nasa.gov/SEbeselm/SEbeselm2001/SE2024Apr08Tbeselm.html and siblings give the same polynomials with k1k_1, k2k_2, ΔT and the solar semi-diameter 3.

Path tables. https://eclipse.gsfc.nasa.gov/SEpath/SEpath2001/SE2024Apr08Tpath.html gives limits and central line at 120-second intervals as preformatted text in WGS 84 4.

Derived repackagings. gmiller123456's repository offers the same data as CSV, JS and JSON 5. Jubier's 5MCSE interface generates per-eclipse KMZ on demand 6. EclipseWise's 2024 bulletin extras include libration values, shadow contact data, central line data and polynomial elements as web pages 7.

Jubier's elements. Each interactive map page embeds its own element array in the HTML, with its own ΔT (69.1 s for 2024) 8.

SVS GIS products

Eclipse Page Files Contents
2017 Aug 21 SVS 4518 eclipse2017_shapefiles.zip, eclipse2017_shapefiles_1s.zip under /vis/a000000/a004500/a004518/ Path and umbra shapes; the _1s set is at 1-second cadence 9
2023 Oct 14 SVS 5073 2023eclipse_shapefiles.zip, 2023eclipse_kml.zip, cities-eclipse-2023.json under /vis/a000000/a005000/a005073/ See layer list below 10
2024 Apr 8 SVS 5073, SVS 5123 2024eclipse_shapefiles.zip, 2024eclipse_kml.zip, cities-eclipse-2024.json See layer list below 10 11

Each 2023 and 2024 zip contains center, duration (30-second isocontours), ppath (5 per cent obscuration contours), ppath01 (1 per cent), umbra_hi (1-second umbra polygons, region limited), umbra_lo (10-second, global), upath_hi and upath_lo 10. The city JSON has LON, LAT, NAME, STATE and an ECLIPSE array of UTC times at 0.01, 50, 100, 50 and 0.01 per cent of maximum coverage for over 32,000 US cities 10. Inputs were SRTM and LRO LOLA plus Kaguya (SELENE), with JPL DE421 on the product pages and DE440 in the paper's appendix, as set out in Wright and Young 2024 10 9. At the time of writing (2026 September) svs.gsfc.nasa.gov refused TCP connections, so the zip URLs could not be verified live and the pages were read from Wayback Machine snapshots dated 2025 10.

Lunar limb and topography data

Which of these grids to use, and what each costs in contact time, is settled in datasets: Watts, Kaguya, LOLA. This section keeps the URLs, sizes and formats.

LOLA GDR. https://pds-geosciences.wustl.edu/lro/lro-l-lola-3-rdr-v1/lrolol_1xxx/data/lola_gdr/ with cylindrical and polar subdirectories 12. The cylindrical IMG directory holds ldem_4.img (2,073,600 bytes), ldem_16.img (33,177,600), ldem_64.img (530,841,600), ldem_128.img (2,123,366,400), four ldem_256_* hemisphere files (1,061,683,200 each) and ldem_1024_<lat>_<lon>.img tiles of about 943,718,400 bytes in 15-degree latitude bands and 30-degree longitude segments, each with .lbl and .xml labels 13. The number in the name is pixels per degree, so ldem_16.img is at 16 pixels per degree, which tomasrojasc/eclipse-2026 quotes as about 1.9 km at the limb 14. Format is PDS3 IMG with detached label.

SLDEM2015. https://pds-geosciences.wustl.edu/lro/lro-l-lola-3-rdr-v1/lrolol_1xxx/data/sldem2015/ with global and tiles subdirectories 15. SVS names this product (LOLA merged with SELENE Terrain Camera) among its inputs 10.

Kaguya (SELENE) LALT. The JAXA DARTS SELENE archive is at https://darts.isas.jaxa.jp/planet/pdap/selene/ and was reachable, though its product pages were not read 16. SVS 4518 cites "JAXA Kaguya stereo imaging" and Jubier's calculator cites "Kaguya's DEM" for limb corrections 9 17.

Lunar orientation. The NAIF PCK directory at https://naif.jpl.nasa.gov/pub/naif/generic_kernels/pck/ was reachable. moon_pa_de440_200625.bpc with frame kernel moon_de440_250416.tf is the pairing for DE440. moon_pa_de421_1900-2050.bpc is the older binary PCK, and it is what tomasrojasc/eclipse-2026 uses to orient the LOLA profile for the libration at contact time 18 14.

Watts charts and Occult limb data. Jubier's Watts-chart corrections are served by his PHP back end and are not downloadable 17. Occult 4 distributes its limb data among 42 downloadable data files installed by the program, not as a standalone dataset 19. SolarEclipseWorkbench bundles lunar_limb_band_v1.bin of undocumented format 20.

Terrestrial elevation

  • SRTMGL1 v003 (1 arcsecond, about 30 m) at LP DAAC: https://lpdaac.usgs.gov/products/srtmgl1v003/ (reachable) 21. SVS used SRTM (SIR-C) 10.
  • Copernicus DEM GLO-30 and GLO-90 on the AWS Open Data Registry: https://registry.opendata.aws/copernicus-dem/ (reachable) 22. Used by carlok/eclipse-3d-sim via OpenTopography and by umbra-eclipse-atlas via Open-Meteo 23 24.
  • EU-DEM 25 m via OpenTopoData is used by eclipsite 25.

ΔT and Earth orientation

  • USNO observed ΔT: https://maia.usno.navy.mil/ser7/deltat.data (text/plain, reachable) 26.
  • USNO predicted ΔT: https://maia.usno.navy.mil/ser7/deltat.preds (text/plain, reachable) 27.
  • IERS finals.all.iau2000.txt: https://datacenter.iers.org/data/latestVersion/finals.all.iau2000.txt (text/plain, reachable), giving UT1-UTC and polar motion 28. Stellarium's default ΔT interpolates IERS values for 2015 to 2033 on top of the Espenak and Meeus polynomial 29.
  • NASA Canon polynomials with the −0.000012932(y−1955)2-0.000012932(y-1955)^2 secular-acceleration correction: https://eclipse.gsfc.nasa.gov/SEcat5/deltatpoly.html 30.
  • Swiss Ephemeris since 2.06 uses Stephenson, Morrison and Hohenkerk 2016 for historical ΔT 31.

Ephemerides

  • JPL DE440 SPK: https://ssd.jpl.nasa.gov/ftp/eph/planets/bsp/de440.bsp (binary, reachable) 32. sunpy's example uses de440s 33. Eclipse-Engine fits elements to DE440s 34.
  • DE421 is what eclipsite, eclipse-2026 and jpatka use, and it is what every SVS product page names, with DE440 in the SVS paper's appendix 10 25 14 35. The NAIF path generic_kernels/spk/planets/de421.bsp returned 404 at the time of writing (2026 September), so the current location of that file was not verified.
  • Swiss Ephemeris files are compressed from DE431 31.
  • NASA's Canon uses VSOP87 and ELP-2000/82 analytic theories rather than a JPL kernel 1.

Sources compared

Dataset Owner Format Resolution or cadence Reachable 2026-09-15
Besselian elements CSV 2 NASA GSFC CSV, 54 columns One row per eclipse, cubic polynomials Yes
SVS 2023 and 2024 GIS 10 NASA SVS Shapefile, KML, JSON 1 s and 10 s umbra polygons Pages via archive only
SVS 2017 GIS 9 NASA SVS Shapefile 10 s and 1 s Pages via archive only
LOLA LDEM 13 NASA PDS PDS3 IMG plus LBL 4 to 1024 pixels per degree Yes
SLDEM2015 15 NASA PDS PDS3 IMG Global and tiles Yes
Kaguya LALT 16 JAXA DARTS Not read Not read Root page yes
SRTMGL1 21 NASA LP DAAC HGT or GeoTIFF 1 arcsecond Yes
Copernicus DEM 22 ESA via AWS Cloud-optimised GeoTIFF 30 m and 90 m Yes
deltat.data, deltat.preds 26 27 USNO Text Observed and predicted Yes
finals.all 28 IERS Fixed-width text Daily Yes
DE440 32 JPL SSD SPK Continuous Yes
moon_pa_de440_200625.bpc, moon_pa_de421_1900-2050.bpc 18 NAIF Binary PCK 1549 to 2650 and 1900 to 2050 Yes

What a developer should do

Download the NASA CSV once and treat it as the regression fixture for the elements stage 2. Fetch the three SVS zips through an archive mirror if the live host stays unreachable and keep them as the fixture for limb-corrected umbra shapes 10. Start limb work with ldem_128.img (2.12 GB). ldem_16.img (33 MB) serves only for smoke tests, since one cell at 16 pixels per degree is worth 2 to 3 s of contact time, as shown in datasets: Watts, Kaguya, LOLA 13. Pair every LOLA use with the PCK of the ephemeris in use, moon_pa_de440_200625.bpc for DE440 18. Pull deltat.data, deltat.preds and finals.all on a schedule and record the fetch date in every product 26 27 28.

What this changes

Nothing in the stage design. It confirms that every input the SVS pipeline used is publicly downloadable, so the SVS products can be reproduced in principle.

Open questions

  • Obtain the SVS shapefile zips themselves and record their coordinate reference system and attribute schema (the pages describe layers but not attributes) 10.
  • Obtain the Kaguya LALT product listing and label format from DARTS 16.
  • Obtain the current NAIF location of de421.bsp, since the standard generic-kernel path returned 404.
  • Obtain the format of SolarEclipseWorkbench's lunar_limb_band_v1.bin and its provenance 20.

References

  1. 1primary Five Millennium Catalog of Solar Eclipses: -1999 to +3000 (NASA GSFC) Read live. States VSOP87 and ELP-2000/82, the ΔT approach by era, n-dot = -25.858 arcsec/cy^2, and links to the CSV of Besselian elements.
  2. 2primary Catalog of Solar Eclipse Besselian elements in CSV format (NASA GSFC) Downloaded 2026-09-15: 5.95 MB, 11,898 data rows, 55 columns including x0..x3, y0..y3, d0..d2, mu0..mu2, l10..l12, l20..l22, tan_f1, tan_f2, t0, dt.
  3. 3primary Besselian Elements for 2024 Apr 08 Total Solar Eclipse (Espenak, NASA GSFC) Read live. Gives the polynomial elements, k1 = 0.272488, k2 = 0.272281, ΔT = 70.6 s, ephemeris VSOP87/ELP2000-85, least-squares fit over six hours.
  4. 4primary Path of Total Solar Eclipse of 2024 Apr 08 (NASA GSFC) Read live. Northern limit, southern limit and central line at 120-second intervals in WGS 84, with diameter ratio, Sun altitude and azimuth, path width and duration.
  5. 5company gmiller123456/FiveMillenniumCanonOfSolarEclipses-Besselian-Elements Read live. Repackaging of the NASA Besselian elements as CSV, JS and JSON; 3 stars; last push 2023-03-10.
  6. 6company Jubier: Five Millennium Canon of Solar Eclipses interface Fetched with curl. States that all data is provided by Espenak and Meeus and that KMZ and maps are generated on the fly for 11,898 eclipses.
  7. 7company EclipseWise: Total Solar Eclipse of 2024 April 08 Fetched live 2026-09-15 with curl. Lists the Eclipse Bulletin extras (libration values, shadow contact data, central line data, polynomial Besselian elements, limb profile).
  8. 8company Jubier: 2024 April 8 Total Solar Eclipse Interactive Google Map Fetched with curl 2026-09-15 (WebFetch refused). The page embeds its own Besselian element array with ΔT = 69.1 s and lists the JavaScript files it loads.
  9. 9primary NASA SVS 4518: 2017 Total Solar Eclipse shapefiles and map Read from a Wayback Machine snapshot (2025). States lunar topography from LRO laser altimetry and Kaguya stereo imaging, DE421, SRTM, and that the limb profile and eclipse calculations are by the visualizer.
  10. 10primary NASA SVS 5073: The 2023 and 2024 Solar Eclipses: Map and Data Read from a Wayback Machine snapshot (2025) because svs.gsfc.nasa.gov refused connections. Lists the shapefile and KML contents and the data sources (SRTM, LRO, DE421).
  11. 11primary NASA SVS 5123: 2024 Total Solar Eclipse map Read from a Wayback Machine snapshot (2025). Same data sources as 5073; links 2024eclipse_shapefiles.zip.
  12. 12primary LRO LOLA Gridded Data Records (PDS Geosciences Node) Read live. Subdirectories cylindrical and polar.
  13. 13primary LOLA GDR cylindrical IMG directory Read live. ldem_4, ldem_16, ldem_64, ldem_128, ldem_256 hemisphere files and ldem_1024 tiles with sizes.
  14. 14company tomasrojasc/eclipse-2026 Read live. Skyfield with DE421, LOLA LDEM_16 limb profile, moon_pa_de421 orientation, Baily's beads per bead; 84 tests; no licence stated.
  15. 15primary SLDEM2015 directory (PDS Geosciences Node) Read live. Subdirectories global and tiles.
  16. 16primary JAXA DARTS SELENE (Kaguya) data archive Reachable (HTTP 200); product pages not read. Entry point for LALT topography.
  17. 17company Jubier: EclipseCalculatorGM3_xSE.js (Solar Eclipse Calculator for Google Maps v3) Source read (198 KB, downloaded 2026-09-15). Change log 2007 to 2016, constants, k1/k2 ratio, Watts and Kaguya limb correction hooks, refraction and elevation handling.
  18. 18primary NAIF moon_pa_de421_1900-2050.bpc Reachable (HTTP 200). Lunar orientation kernel used by repositories that build limb profiles.
  19. 19company Occult v4 (David Herald) home page Fetched with curl 2026-09-15. Feature list, C#/.NET 4.5, 42 data files, installer sizes. Eclipse-specific help is inside the Windows help file and was not read.
  20. 20company AstroWimSara/SolarEclipseWorkbench Read live. Astropy and IERS for ΔT, solar radius 959.95 arcsec, bundled lunar limb band file, SPICE kernels; GPL-3.0; 20 stars.
  21. 21primary NASA LP DAAC: SRTMGL1 v003 Reachable (HTTP 200); product page not read in full.
  22. 22primary Copernicus DEM on the AWS Open Data Registry Reachable (HTTP 200); page not read in full.
  23. 23company carlok/eclipse-3d-sim Read live. Astronomy Engine circumstances plus DEM ray-casting (Copernicus 30 m via OpenTopography); no licence stated.
  24. 24company plhery/umbra-eclipse-atlas Read live. Uses @astronomy-bundle/solar-eclipse with NASA Canon elements, Copernicus DEM skyline; MIT.
  25. 25company Xeratec/eclipsite Read live. Skyfield DE421 plus NASA Besselian cross-check (0.36 s mean difference), EU-DEM 25 m skyline, RMS 0.60 s against IGN durations; MIT.
  26. 26primary USNO deltat.data Reachable (HTTP 200, text/plain). Observed ΔT table.
  27. 27primary USNO deltat.preds Reachable (HTTP 200, text/plain). Predicted ΔT table.
  28. 28primary IERS finals.all (IAU2000) Reachable (HTTP 200, text/plain). UT1-UTC and polar motion.
  29. 29company Stellarium src/core/StelCore.cpp (ΔT algorithms) Read from the same clone. Default ΔT is EspenakMeeusModified; describes the Espenak and Meeus polynomial and its use in the Canons.
  30. 30primary Polynomial Expressions for Delta T (Five Millennium Canon) Read live. Piecewise polynomials by year range and the secular-acceleration correction c = -0.000012932 (y - 1955)^2.
  31. 31company Swiss Ephemeris General Documentation Read live. Licensing (AGPL or professional licence), DE431 basis and time range, ΔT model since 2.06 based on Stephenson, Morrison and Hohenkerk 2016.
  32. 32primary JPL DE440 planetary ephemeris (SPK) Reachable (HTTP 200, binary).
  33. 33company sunpy gallery: Obtaining solar-eclipse information Read live. Uses de440s and ITRS observer positions.
  34. 34company RHerAle/Eclipse-Engine (eclipseradar.com engine) Read live. Besselian geometry, elements fitted to DE440s, terrain skyline from DEM and OSM, AGPL-3.0, last push 2026-09-14.
  35. 35company jpatka/Eclipse-Explorer Read live. Skyfield DE421, refraction; no validation; MIT.