A supplement to the brief in-app Instructions (Info tab). Covers every feature in depth, with examples.
Who doesn't love an eclipse? Earth–Moon–Sun all in a straight line? Amazing. The Sun using the Moon to point at a specific place on land? Even better. So here is a tool to help you get to that spot, where you can witness the sky while, like a giant coronal iris with a razor-sharp pupil at its centre, the sky stares back at you.
In case you want to go back in time, this app covers ~11,800 solar eclipses — a five-millennium range. Pick an eclipse, click a location, get exact local circumstances — sunrise/set, contact times, sun position, cloud outlook, terrain shadows. Works fully offline once installed, which is the point: it's built for the field.
Rich search is important. I saw an eclipse when I was a kid. When's the next eclipse on my birthday? When's the next eclipse in Hanimadhoo? Was there an eclipse on my birthday in Hanimadhoo when I was a kid?
Type any combination of these into the search box, in any order, separated by spaces:
| Category | Examples |
|---|---|
| Today | todaynowtoday+1994-now |
| Year | 20262026-20301994+1994-after 2100before 50044BC10BCE-10CE |
| Month | augaugustNov28 |
| Saros | saros 126s126 |
| Type | totalannularhybridpartial |
| Obscuration | >8050+<3095- |
| Location | parisjapan(44.858, 0.082)(51°30'26"N, 0°07'40"W) |
Example: total 1900-2026 Burgos — shows both total eclipses in Burgos, 121 years apart.
A country stands for all of itself: chile total asks whether the eclipse reached anywhere in Chile. Names take several forms — usa, us, United States, United States of America, and the two- and three-letter codes.
Four things differ from a city:
armenia means the city in Colombia; armenia country means the country.france. The far-flung parts are searchable separately: french guiana, réunion, martinique, caribbean netherlands. Accents optional.Multi-word names work as you'd write them: new york, ho chi minh, cape town. You don't need quotes.
paris france total works too — the country just says which Paris, and filters nothing.
Clicking the map replaces whatever place you'd typed, keeping the eclipse type.
total — eclipses which are total anywhere.total paris, chile total — only eclipses which appear total from that place.italy total >90 — adding an obscuration widens it back to total anywhere, kept only where your place sees at least that partial percentage. In August 1999 the path passed just north of Italy, so italy total finds nothing while italy total >90 finds it.The globe itself, and the controls that live on top of it. On desktop it's the permanent centre view; on mobile it's the Map tab.
◐ Terrain shadows — so you can see where the eclipse will actually be viewable given the local terrain.
☁ Cloud cover — three data sources, one button. It reveals:
☺ Favorability — the other two overlay buttons each show you one ingredient. This one blends them into a single answer to “how good is this spot for watching this eclipse”, painted along the central path only, blue for better and red for worse. Total and annular eclipses only; the button does nothing for a partial one, which has no central path.
Everything the app knows about the selected eclipse, in two parts: what it looks like from your location, and the event's global facts, which don't depend on where you're standing.
Shown once you've set a location (search by coordinates, or click the map). A summary — duration, magnitude, obscuration, sun position at maximum
Favorability computes a summary of the rows above rather than another measurement — the same blended score the ☺ overlay paints, for the spot you have selected. Hover it (or tap it) for the three numbers behind it. It appears only inside the central path, where the score means something.
The row above it, Clear sky, is the odd one out: it says nothing about the eclipse, only about your chances of seeing it. It's the share of the time this spot has been historically cloud-free at that time of day and that time of year, from the satellite record. Higher is better, like everything else in the block. It is not a forecast — for an eclipse in 2085 no such thing exists, and even for next month this is a long-run average rather than a prediction.
C1 (partial begins) → C2 (totality/annularity begins, umbral events only) → MAX (greatest eclipse) → C3 → C4, each with sun altitude and azimuth. Click any row to jump the sky-tracker (and terrain-shadow scrubber, if it's open) to that instant.
Each row carries a small icon showing the Sun–Moon overlap oriented as you'd actually see it — the angle is measured clockwise from your zenith, so the icon tells you which side of the Sun's disc the Moon is covering at that moment, not just that a contact is happening.
Click the column header to switch every time in the table (and the shadow-scrubber clock) between local time and UT. Persists across sessions.
A small interactive sky diagram — the Sun's path across your sky through the whole event, drawn to true scale, so distances on it are real distances in the sky. Drag its slider to scrub a Sun marker along the arc and watch the Moon's bite grow and shrink at each instant, in sync with the contact-times table above.
Where the eclipse is total at your location, the planets and the bright stars appear around the Sun between second and third contact, each where you would actually see it.
Reference facts about the eclipse itself, independent of any location: time and place of greatest eclipse (UT), sun altitude/azimuth there, magnitude, path width, longest duration (and where), Saros number, and ΔT used for the calculation.
Three icons sit beside the date:
The diamonds along the centreline — one roughly every 100 km — are the useful part. Each one already carries its own contact times: click it in Google Earth and the balloon gives C1 to C4, duration, sun altitude and azimuth, and obscuration for that exact spot, in UT and in local time.
Your personal list of saved/seen eclipses.
Per-entry controls, left to right:
| Icon | Action |
|---|---|
| → | Mark as seen — the flag fills in once toggled on. |
| Overwrite the entry's saved location with the map's current pin. | |
| Remove the eclipse from the list. | |
| Jump to — restores this eclipse and its saved location on the map. | |
| Checkbox — include this eclipse on the poster map (below). |
Toolbar, below the list:
| Icon | Action |
|---|---|
| Make map — see Poster maker, below. | |
| Select all / clear selection for the poster (a dash instead of a tick means only some rows are picked). | |
Export log — downloads your whole log as a dated .json file. This is your entire backup story, so do it before switching devices or clearing browser data. |
|
Import log — merges a previously exported .json file back in (adds new entries, updates matching ones). |
Tap Make map to open a full-screen "umbral paths" map built from your Log selection — every checked eclipse's path on one world map. If nothing is checked, it uses your whole log. Options:
Good for a "my eclipses" wall map or literally printing on a shirt.
This manual, but shorter — the in-app quick reference, plus the home-screen install link.
fonts/OFL.txt).Every curve is computed to within a few metres of its exact geometric definition — centreline, umbral and penumbral limits, sunrise/sunset curves and the maximum-on-horizon curve, all ~3 m or better. Between drawn points a line can bow a little further, up to ~10 m.
Eclipses before 1900 or after 2050 are subject to variability in ΔT.
No lunar limb correction is applied.
My name is Guy, and I have been following eclipses since a fateful camping trip back in May 1994. We all ate mushrooms and sat in a circle with drums between our knees, silver glasses on our faces, grinning like fools and staring upwards at the ring of fire. That kind of sealed the deal, and certainly changed my life. Since then, I have always had a direction — an endless series of predictable glorious events — to pursue: across mountains, jungles, and deserts, to the very farthest corners of the globe.
Although there are many eclipse-adventure-planning tools out there (Thank you, Mr. Espenak! Merci, M. Jubier!), I still missed certain features: search-by-date (all the eclipses on your birthday), search-by-location (what, Ouagadougou went 894 years without a TSE?!), search-by-vibe (was there a total eclipse right near but not in Oslo sometime in the 50s?), historical cloud data overlays (did he just use the C-word?), shadow-mapping from local topographies (d'oh that hill is in the way!), and offline map caching for in-the-field use. This app tries to cover all the bases in one convenient package, to help plan syzygystic adventures more efficiently. I also learned a ton about Besselian geometry while making it, which is always so much fun.
On a phone, add it to your home screen. Use your browser's share button and choose "Add to Home Screen". Installed, it runs full-screen, keeps its offline data, and behaves like an app rather than a web page — which is the point, since it is built to work in a field with no signal.
Tuned to Chrome + iOS and never tested on Android — if you have any suggestions or find any bugs, drop me a line — and don't stare at the sun!