Topline
There is no shortage of maps showing the path of totality for the total solar eclipse in Europe on Aug. 12, with NASA, the European Space Agency and eclipse cartographers all making them widely available. However, not all eclipse maps are created equal — and for anyone hoping to witness totality from close to the edge of the path, the details matter more than ever. A new interactive eclipse map and the Eclipse Countdown App have been computed by a team of scientists and eclipse chasers that uses terrain data. Where most maps suggest that totality will be brief, there’s now a risk that it won’t happen at all. It’s the latest version of a map that went viral before the 2024 total solar eclipse in North America when 15 places lost totality.
Key Facts
A total solar eclipse is coming to Europe, but only to a narrow path across parts of eastern Greenland, western Iceland and northern Spain on Aug. 12. The edge also crosses three tiny bits of Portugal.
The path of totality is about 180 miles wide. If you’re not in the path of totality, you cannot experience a total solar eclipse.
The precise geometry of the path of totality — the moon’s shadow cone as it tracks across a rotating Earth — traditionally depends on calculations made using a set of values called Besselian elements. The distance of the moon from the Earth and the exact shape of the moon —but also of the sun — are critical.
However, the value for the sun’s diameter appears to be wrong, leaving eclipse maps — projections of the moon’s shadow — slightly askew. Neither do most eclipse maps take into account how shadows fall on terrain. The new map is computed using the IQP eclipse computational method that accounts for an improved value for the eclipse solar radius as well as the exact shape of the moon and topography.
Anyone viewing any stage of the partial solar eclipse must use ISO 12312-2-certified eclipse glasses to view the event safely. Only those within the path of totality will be able to remove their eclipse glasses, and then only during totality itself. That will last up to 2 minutes 18 seconds.
Why The Edge Of Totality Matters
At the centerline of a path of totality, the observer witnesses the longest totality possible. Right at the edge, it’s just a few seconds. Just beyond the edge, there is no totality. For most eclipse chasers traveling well inside the path of totality, precisely where the edge of the path is makes no difference. However, for those living near the edge, it could determine whether they experience totality or miss it altogether. That is particularly true in Spain, where some of the most populated areas are close to the eclipse limits. “One of the main places in Spain where the limit lines cross well populated areas are the northern suburbs of Madrid and Bilbao, coincidentally both near their respective airports,” said Luca Quaglia, an eclipse chaser and researcher based in Australia, in an email. “For people living in those suburbs and not traveling, being on the wrong side of the limit lines will make a difference.” It’s also down to an inaccurate figure for the solar radius, which can make eclipse maps out by as much as about 2,000ft. (600 meters) at their edges.
Putting Portugal On The Map
The new edge map also underscores that Portugal deserves to be mentioned much more when discussing this eclipse. The southern edge of the path crosses two tiny villages of Portugal (Rio de Onor and Guadramil) on most maps, but on the new map, it crosses three — albeit it is a mountainous sliver with no settlements.
Why Mountains Can Matter As Much As Clouds
In northern Spain and Portugal, the eclipse will occur near sunset, with the sun just a few degrees above the horizon. That creates the possibility of a spectacular “sunset eclipse,” in which the corona glows above distant hills, but also risks. A mountain and/or a single cloud bank, making location choice critical. Eclipse chasers are using resources like The Eclipse App, SunsetAtlas, Eclipse Horizon, Instituto Geográfico Nacional and TPE, all of which can help make sure they’ll be able to see the eclipse from specific places. The Besselian Elements team has added terrain shadows at totality time, but also a way of recognizing that the clouds blocking an eclipse may not actually be above the observer. “A weather forecast for the vertical of the observing site might be misleading as the weather to look for will actually be at a noticeable distance away,” said Quaglia. “On our website and on the map we have provided weather data at 18h UTC, as the days go by, for a range of meteorological variables to have everything on one page.” Crucially, it includes a “line of sight” cloud cover forecast to capture the probability of a real-life view of the eclipsed sun.
Beginning this week, the website will publish successive forecasts for 18:00 UTC without removing previous runs, allowing eclipse chasers to see whether weather patterns are becoming more reliable or remain uncertain. Areas where forecasts consistently predict clear skies — or persistent cloud — will become increasingly obvious as eclipse day approaches.