Eclipse map

[SBL]

Dear friends, I’m not sure if I could count on your help to solve a GIS problem: I belong to a group of amateur astronomers in Spain, and as you may know, next August there will be an eclipse that is particularly well visible from our region (northwest Spain). There are government plans to coordinate the event logistics, which will attract the attention of thousands of people from all over the world. We are already being asked which will be the best locations to observe it or to conduct scientific studies. The problem with this eclipse is that its maximum development occurs quite late, and from some locations the sun will have already set by that time. I’m trying to obtain a map that indicates which areas of my province (León) will already be in shade at that moment due to the local terrain relief, to warn prospective observers. I know one can create visibility maps for objects located at given geographic coordinates (for example, for landscape impact studies), but I don’t know how to determine the visibility area of a sun located at certain altitude-azimuth coordinates. The concrete data would be: Altitude (height above the horizon): 10°; Azimuth (direction above the horizon): 281° (approximately west); Time of maximum eclipse: 20:29 (CEST), 12 August 2026. My goal, more than generating a map, would be to create a kind of Google Earth plugin or similar (to be inserted in a web) so that each interested person could query online the visibility of the event from their particular position. Thanks if you could guide me in that sense.

[CodyPatterson]

Hey @SBL 

My previous company did something similar, but we used this map here: https://shademap.app/@40.13774,-4.04011,7.6701z,1767717458444t,0b,0p,0m

It lets you see a decent idea of where the shade will be at that time, we sent the link out in a social media post, and had people enter their addresses and then find the time like that, this is a screenshot:

There is another that you can try, but it unfortunately doesn't appear that it renders shadows: https://www.suncalc.org/#/40.417,-3.1215,8/2026.01.06/14:33/1/3

What it does show is the position of the solar eclipse which could be handy!

Cody

[VenkataKondepati]

I am not an expert on this topic, but you can try the following:

You don't need a complex "visibility" analysis; you just need to treat the sun as a light source. Here is the reality of how to map those shadows for León:

• The Analysis: Use the Hillshade or Shadows tool in Pro or QGIS. Set the Azimuth to 281° and Altitude to 10° using a high-res DEM. This creates a "shadow map" where terrain blocks the sun.

• The Web Tool: The easiest "plugin" is the ArcGIS 3D Scene Viewer. Add your terrain and use the Daylight Widget. Set it to August 12, 2026, at 20:29, and it will render the shadows dynamically for any user.

• The Alternative: Export your shadow raster as a KML/KMZ so users can toggle it directly in Google Earth to check their specific coordinates.

Don't forget that at 10°, atmospheric refraction is a factor. Build in a small safety buffer so you don't accidentally tell someone they'll see the sun when they're actually in the shade.