Local eclipse calculations
Local circumstances are calculated from latitude, longitude and optional elevation with Astronomy Engine. The result includes eclipse type, obscuration, partial contacts, annular/total central contacts where available, maximum eclipse, central-phase duration, Sun altitude and Sun azimuth. The event selector uses separate search windows so February 6 and August 2, 2027 cannot be silently confused.
Why coordinates stay visible
A city is not a single point. Two observers on opposite sides of the same metropolitan area can receive different contact times and totality durations. Every location guide therefore publishes its reference coordinate and lets the user replace it.
Annular versus total event logic
The February 6 event is annular, so Eclipse Wayfinder reports annularity rather than totality and does not send users into August-specific totality tools. The August 2 event is total and therefore supports the Totality Finder, Totality Gain and destination-comparison workflow.
Path geometry and nearest totality
NASA publishes the August 2, 2027 central line and path limits at regular time intervals. Eclipse Wayfinder stores a reduced centerline series to identify useful search directions. It then repeatedly calculates local eclipse circumstances along candidate routes to locate the transition from partial to total.
Why Totality Finder adds a buffer
Lunar mountains and valleys can shift the real totality limit relative to a smooth-limb prediction. A path-edge coordinate is therefore a poor travel target. Totality Finder shows the modelled boundary estimate and a separate point 5 km farther inside the path.
Totality Gain optimization
The gain calculator samples a great-circle route from the starting point toward a nearby centerline target. It records totality duration along the route and reports the extra seconds gained within the chosen radius. The result is an astronomy optimization, not a road route.
Path-margin estimate
Path margin uses the observer's distance from the interpolated centerline and the local interpolated path width. It is a planning indicator that describes how far inside the approximate corridor a point sits. It is not a substitute for the direct local eclipse calculation.
Viewing score: 70 astronomy/planning points plus 30 climate points
| Component | Maximum points | Method |
|---|---|---|
| Totality duration | 25 | Calculated |
| Historical solar clarity | 25 | NASA POWER August 2001–2025 proxy |
| Path margin | 8 | Active |
| Sun altitude | 7 | Active |
| Accessibility | 12 | Curated structural baseline |
| Accommodation | 8 | Curated structural baseline |
| Mean-temperature comfort | 5 | NASA POWER August 2001–2025 proxy |
| Relocation flexibility | 5 | Curated structural baseline |
| Viewing environment | 5 | Curated structural baseline |
Historical climate is not a forecast
The climate pipeline uses one fixed comparison period: August 2001–2025. For each reference coordinate, NASA POWER supplies all-sky and clear-sky surface shortwave irradiance, 2 m air temperature and 2 m relative humidity. The solar clarity proxy is simply all-sky irradiance divided by clear-sky irradiance and expressed as a percentage. A value of 82 therefore contributes 82/100 to that score component; it does not mean an 82% chance of cloud-free eclipse weather.
The mean-temperature comfort score gives full credit from 18–28°C and then declines as the long-term August mean moves outside that band. It is a travel-planning proxy, not a heat-health model. Humidity remains visible but is not hidden inside the comfort score.
Live conditions stay separate
Weather forecasts, road closures, border rules, hotel availability and crowding can change. Eclipse Wayfinder does not bake those volatile facts into a static score months in advance. They should be rechecked with current sources close to the event.
Reproduce the decision
Use Eclipse Finder for the local calculation, Totality Finder for path entry, Totality Gain for distance payoff and the Comparator for destination trade-offs.
How conflicting values are handled
Different eclipse websites can publish slightly different city times because they may use different coordinates, ephemerides, lunar-limb treatments or rounding rules. Eclipse Wayfinder does not choose a value simply because another website is popular. The first check is whether both sources use the same observer coordinate and the same event definition. The calculation method and reference coordinate stay visible so differences can be reproduced.
Primary checks use NASA GSFC eclipse references alongside the documented Astronomy Engine calculation method.
Corrections and methodology changes
If a reproducible calculation appears wrong, email contact@eclipsewayfinder.com with the coordinate, page URL and comparison source. Material methodology changes should be reflected here and on the data-sources page. Read the disclaimer for the limits of astronomy, climate and travel-planning outputs.