Sources and credits
Every figure on the site comes from a source you can check. Here are the 56, grouped by topic and with what they support.
Moon data
- NASA NSSDC — Moon Fact Sheet
Distance, diameter, orbital inclination, recession of 3.8 cm/year.
- NASA Science — Moon
General data, synchronous rotation, and formation.
- NASA GSFC — Eclipses and the Moon's Orbit
Extreme perigee and apogee (356,355 / 406,725 km).
- NASA SVS — Moon Phase and Libration
Phases, libration (59% of the visible surface).
Planets and escape velocity
- NASA NSSDC — Planetary Fact Sheet
Escape velocities and diameters of the planets.
Eclipses and recession
- NRAO — When did the first annular eclipse occur?
First annular eclipse, ~1.6 billion years ago.
- Smithsonian NASM — Limited Edition: Total Solar Eclipses
Last total eclipse, within ~600 million years.
- NASA NSSDC — Sun Fact Sheet
Apparent diameter of the Sun (0.5331°).
Tides and the ocean
- NASA — Dissipation of Tidal Energy
~1 TW of tidal energy dissipated in the deep ocean.
- NOAA — How much oxygen comes from the ocean?
Nearly half of Earth's oxygen comes from the ocean.
- NOAA — What causes tides
The Sun's tidal force is about half that of the Moon.
- University of Hawaiʻi — Tide Formation: Tide Height
Equilibrium tide of ~0.5 m: the basis for showing how exaggerated the tide illustration is.
- WHOI — Black Sea Studies
The Black Sea, the world's largest anoxic basin.
- Klatt et al. 2021 — Nature Geoscience
Longer days and oxygen release by cyanobacteria.
The early Earth
- Eulenfeld and Heubeck 2023 — JGR Planets
3.2 billion years ago, the Moon was at ~70% of its current distance and the day lasted ~13 h.
- Catling and Zahnle 2020 — The Archean atmosphere (Science Advances)
An oxygen-free atmosphere with much more CO₂ and methane, and a temperate climate.
- Homann et al. 2018 — Nature Geoscience
Microbial mats in the tidal flats of the Moodies Group (3.22 billion years ago).
- Astrobiology — Were Earth’s blue oceans once green?
Greenish sea due to iron (Matsuo et al., Nature Ecology & Evolution).
Axial tilt and the Moon
- NASA Science — Milankovitch (Orbital) Cycles and Their Role in Earth's Climate
The current tilt (~23.4°) and its 41,000-year cycle between 22.1° and 24.5° (3.8).
- Laskar, Joutel & Robutel 1993 — Stabilization of the Earth's obliquity by the Moon (Nature 361)
The Moon stabilizes Earth's axial tilt; without it, a chaotic zone from ~0° to ~85° (3.8).
- Lissauer, Barnes & Chambers 2012 — Obliquity variations of a moonless Earth (Icarus 217)
An Earth without the Moon: the tilt oscillates more, but within a band of ~20–25° over hundreds of millions of years (3.8).
- Li & Batygin 2014 — On the Spin-axis Dynamics of a Moonless Earth (ApJ 790)
An Earth without the Moon: chaotic drift would be slow enough not to prevent life (3.8).
- Néron de Surgy & Laskar 1997 — On the long term evolution of the spin of the Earth (A&A 318)
The future of Earth's axis: entry into the chaotic zone within 1,500–4,500 million years (3.8).
- Laskar et al. 2004 — Long term evolution and chaotic diffusion of the insolation quantities of Mars (Icarus 170)
Mars's chaotic tilt: average ~38°, maximum ~82° (3.8).
- CU Boulder / NASA MAVEN — How Mars' atmosphere was lost to space (2017)
How Mars lost its atmosphere: the solar wind, after its magnetic field shut down (3.8).
- NPR (2018) — Scientists find what could be a history-making moon
David Kipping's quote about the “twin moon” of a twin Earth (3.8).
- Astrobiology — Giant doubts about giant exomoons (2024)
No confirmed exomoons; the two candidates remain under debate (3.8).
Calculations and validation
- astronomy-engine (Don Cross)
Phases, illumination, rise and set, positions of the Sun and Moon.
- JPL Horizons
Reference ephemerides used to validate the calculations in automated tests.
- Jean Meeus — Astronomical Algorithms (2nd ed., Willmann-Bell, 1998)
Position angle of the bright limb (48.5) and parallactic angle (14.1).
- @photostructure/tz-lookup
Time zone from coordinates.
Software
- Astro
Site generation.
- React
Interactive components.
- GSAP + ScrollTrigger + SplitText
Animations and scrolling sections.
- Lenis
Smooth scrolling.
- Vitest
Automated tests.
Images
NASA photos and visualizations are in the public domain. Recreations of scenes that no one has been able to photograph are made with AI from real references and checked against the scientific literature. The diagrams are our own.
- NASA GSFC Scientific Visualization Studio — First Quarter
The Moon in the header: a visualization with real LRO data (LOLA altimeter and LROC camera), not a photograph. Earthshine added locally from the same image.
- NASA — Apollo 11 retroreflector (AS11-40-5952)
Photo of the laser ranging experiment in block 06.
- NASA — The Blue Marble (AS17-148-22727)
Earth in “The Distance, to Scale” and reference for the tide illustrations.
- NASA SVS — CGI Moon Kit (Ernie Wright, Noah Petro)
The fully illuminated near side (phases and diagrams) and the global LROC color and LOLA relief maps of the 3D Moon on the homepage, “Your Moon Today,” and “The Full Cycle.”
- NASA SVS — Blue Marble Next Generation (Reto Stöckli)
Earth viewed from the North Pole in the tide and recession diagrams (projected locally).
- NASA/JPL — Mercury (MESSENGER, PIA15160), Venus (Mariner 10, PIA23791), Mars (Viking, PIA00407)
Planets in “The Distance, to Scale”.
- NASA/ESA Hubble — Jupiter, April 3, 2017 (GSFC_20171208_Archive_e000103)
Jupiter in “The Distance, to Scale” when 3D is not available (fallback).
- NASA/JPL — Saturn with its rings (Cassini, PIA06193), Uranus and Neptune (Voyager 2, PIA18182, PIA01492)
Planets in “The Distance, to Scale” when 3D is not available (fallback); Saturn’s rings, tilted 74° so they don’t encroach on their neighbors.
- HYG Database v4.2 (David Nash) and IAU Catalog of Star Names
Stars down to magnitude 6 and their names in “The Sky Tonight”.
- IAU and Sky & Telescope constellation figures (Alan MacRobert)
Lines for the 88 constellations in “The Sky Tonight”: our own set, compiled from several sources following the IAU figures.
- Stellarium, “modern” sky culture (Stellarium team, CC BY-SA 4.0)
Line figures for Virgo and Capricorn, so they match the classical maiden and sea goat.
- vue-skynight (Sergioluis Mendiola Alcalde) — projection, Moon and twilight brightness
Rendering engine for “The Sky Tonight”: stereographic projection, lunar glow, sky color, and twilight.
- NASA SVS — Moon Phase and Libration, 2026
Image of the Moon according to its phase in “The Sky Tonight”.
- NASA/Goddard SVS — Deep Star Maps 2020 (Gaia DR2: ESA/Gaia/DPAC)
Full-color map of stars and the Milky Way for “Photo Mode” (its stars enhanced as in a developed photo with positions, brightnesses, and colors from Gaia DR3, ESA/Gaia/DPAC, CC BY-SA 3.0 IGO), and Milky Way map (just the diffuse glow, with the Magellanic Clouds) for “The Sky Tonight,” processed to resemble what the eye sees (almost colorless, low contrast, narrow band) and smoothed with AI (GPT Image 2.5), preserving the map’s brightness and shape.
- ESO — Magellanic Clouds (eso1914a, eso1714a)
Magellanic Clouds in “The Sky Tonight” only if the Milky Way layer cannot load (fallback).
- Solar System Scope — planetary textures (based on data from MESSENGER, Viking, Cassini, and Hubble)
Global maps of the seven planets and of Saturn’s rings in the 3D version of “The Distance, to Scale”.
- NASA/SDO — Spotless Sun (PIA21569)
Sun texture in the top-down view of the phase cycle—with a photographic glow added with AI (GPT Image 2.5); the disk is NASA’s—and in the geometric reference for the eclipse photos (colored as visible light; the original is ultraviolet).
- NASA/Hubble — Mars at its closest approach in 2003 (J. Bell, M. Wolff)
Photograph of Mars with its south polar cap (3.8).
- NASA — 2017 Total Solar Eclipse (AFRC2017-0233-005)
Real corona reference for the total eclipse recreation.
- GPT Image 2.5 (OpenAI, via fal.ai)
Recreations of Earth and the Moon at different distances, of the Moon breaking apart at the Roche limit, of Earth 3.2 billion years ago, of the ocean with and without mixing, of the three eclipses (with the Moon/Sun ratio calculated, corrected locally after generating them), and of the water in the tidal bulge and the level gauge (on a measured silhouette of the diagram), and of the mythological figures of the constellations (drawn over the projection of their own stars).
Additional credits
- Leinert, Ch., et al. (1998), “The 1997 reference of diffuse night sky brightness”, Astron. Astrophys. Suppl. Ser. 127, 1–99
Surface brightness of the zodiacal light (Table 17, V band), used by the sky simulation.
Images and videos generated with AI (GPT-Image / Seedance).
Developer & company
- Developer
- github.com/MendiolaSergioluis
- Company
- atacamastargazing.com
The astrotourism company behind these sky observations.
© 2026 Sergioluis Mendiola Alcalde
Source code under the MIT License — Copyright (c) 2026 Sergioluis Mendiola.