A high-level overview: observer-specific solar geometry, global DEM terrain sampling, horizon line-of-sight checks, and an intuitive score designed to compare observing locations.
We evaluate NASA/GSFC Besselian eclipse elements for each observer coordinate to estimate local contact times (C1, C2, C3, C4), eclipse type (Total, Annular, or Partial), solar altitude, azimuth, magnitude, and central-phase duration.
We sample Mapzen Global Terrain tiles from the AWS Open Data Registry across a 400 km range and a 90° field centred on the Sun. A denser ray follows the exact solar azimuth so distant ridges are checked where they matter. Tile zoom 10 gives a ground pixel size of roughly 117 m in northern Spain; source DEM resolution and vertical datum vary by region. This is planning-grade terrain, not a land survey.
We cross-check the solar and lunar trajectory against your site's local terrain profile. This ray-tracing step is vital for sunset eclipses (like August 12, 2026 in Spain), identifying if a mountain ridge will occlude the Sun during maximum totality before atmospheric sunset.
The combined data produces a single 0–100 Visibility Score. It weighs totality duration, solar altitude above obstacle lines, obscuration percentage, and horizon clearance into an objective metric for comparing candidate viewing spots.
An interactive skyline preview renders the landscape profile and solar path dynamically. Scrubber controls allow you to step through C1 to C4 moment-by-moment to preview exactly where the Sun will be relative to local peaks.
First, explore candidate regions using the macro visibility score map to find high-potential zones. Then inspect the DEM horizon profile to see whether sampled mountain terrain clears the lower edge of the solar disk at maximum eclipse.
Compare entire provinces and path centers at a glance.
Inspect the sampled terrain source, local ground-pixel size, range, and line-of-sight result.
Drop a pin on the exact ridge, beach, hotel or rooftop you're considering and inspect its exact contact timings, mountain and building clearance, and live weather forecast for eclipse day.
The Visibility Score synthesizes multi-layered calculations into an actionable 0–100 signal for evaluating observation options.
Distinguishes whether a location experiences total eclipse, annular ring, partial obscuration, or lies outside the usable path.
Evaluates the duration of the central phase, rewarding locations closer to the centerline with maximum duration.
Factors in eclipse magnitude and peak percentage of the solar disk occluded by the lunar silhouette.
Compares the apparent lower solar limb against curvature- and refraction-adjusted terrain. Marginal results still require an on-site check for trees, buildings and local DEM error.
Eclipse circumstances use NASA/GSFC Besselian elements. Terrain elevations come from Mapzen Global Terrain Terrarium tiles hosted as AWS Open Data; Mapzen combines multiple open elevation sources, so source resolution and vertical datum vary by region. The horizon model includes Earth curvature, a standard 0.13 terrestrial-refraction coefficient and a 1.7 m eye height. It does not include buildings, trees, snow depth or unusual atmospheric refraction; verify marginal views on site.
SunEclipses is a planning tool, not a land survey. Verify marginal sightlines on site, along with real-time weather forecasts, road access, and local safety rules before traveling on eclipse day.