About Totality Trail

Totality Trail is a free, educational visualiser of solar eclipses from 1999 to 2100 on a turnable globe: where the shadow goes, how much of the Sun is covered at your place, when it starts, peaks and ends, and how to watch safely. It is meant for explanation and planning, not as an official source for navigation or safety.

How the app calculates

Everything comes from one shared solution of the Besselian elements NASA publishes for each eclipse: the path of the shadow, the contacts at your place, the obscuration, the altitude of the Sun and the speed of the shadow. That is the same method the professional canons use. What is not modelled: weather, terrain, the height of your horizon and the exact position of the observer, so treat the times as good to about a second and the edges of the path as good to a few kilometres.

How a solar eclipse works, and what the contacts mean, is explained on the page About eclipses.

What the counter keeps, as day totals and never per person: how many pages were opened, how many different visitors that was, and how many of them came back the same day. It also counts which site people arrived from, their browser and platform, roughly how wide their screen is and whether they hold it upright or sideways, each in a handful of fixed groups. The page you came from is reduced to the site name, and your IP address is never stored. Bots are counted separately, and so is the app embedded on other sites, with the name of the site it hangs on. No location, no course through the site, nothing per person. The counting happens on our own server, the numbers are for us alone, and we do not sell visitor data or share it with anyone. Nothing is stored on your device, and because the daily salt changes, even we cannot tell the next day who anyone was.

Data and licences

The Besselian elements come from the NASA Eclipse Web Site (Fred Espenak), the coastlines and the country outlines from Natural Earth; both are in the public domain. The city index is built from GeoNames (CC BY 4.0).

Satellite imagery: NASA Blue Marble, served through NASA GIBS.

The average cloud cover along the path comes from NASA POWER, which serves the monthly cloud climatology of CERES SYN1deg: satellite observations over 2001 to 2020 at one degree. The values are baked in when the app is built, roughly every hundred and ten kilometres along the path, interpolated to the day between the two nearest monthly means. Each point uses the hour at which the shadow passes there, in local solar time; where that hour is missing, the mean over the whole day remains. It is a climatological average for that place and that date, not a forecast, and the app makes no weather requests while you watch. A point you pick yourself, away from the path, gets its value from two grids the app fetches only once you open that graph: the monthly means at one degree and the daily cycle at five.

The two typefaces, DM Mono and Outfit, are served from this site under the SIL Open Font License.

NASA: Besselian Elements · Natural Earth · NASA GIBS · GeoNames · NASA POWER · SIL Open Font License

Privacy

There is no account, no cookies and no tracking across sites. The only things kept in your own browser are your preferences (eclipse, place, language, speed, map style) and the city index; clear the site data and they are gone. Visits are counted on our own server, without cookies and without anything on your device; the paragraph below says exactly what that counter keeps. Satellite tiles are fetched from NASA GIBS while the satellite view is on, so NASA sees those requests as it would for any map. A share link contains only the view you share.

Accessibility

Every control works with the keyboard, has a name for a screen reader, and the panels announce changes only while the animation is paused. Colours are chosen for legibility against the dark background. Two deliberate limits: picking a free point on the globe has no keyboard equivalent yet (type a city or coordinates instead), and pinching to zoom the page is switched off on the map page so that the map can be pinched; the text pages zoom normally.

Who makes it

Totality Trail is a side project of one developer in the Netherlands, built out of curiosity about the eclipses of 2026 and 2027 over Europe. It is not affiliated with NASA or any observatory. Mistakes are possible; the Versions page shows what changed and when. Suggestions and error reports are welcome.