Local Sun and globe sky comparison
Set three observing places and one UTC instant. Compare their solar directions with a nearby source moving on an explicitly defined north-polar plane.
Compare all three sites at 2026-03-20 12:00 UTC. The nearby source follows the entered north-polar map ring and longitude; its elevation remains positive at every finite distance. A beam can extinguish its light but does not put the source below the planar horizon.
| Site · lat, lon | Local altitude / azimuth | Sky altitude / azimuth | Local source angular size | Local beam |
|---|---|---|---|---|
| A · 51.478°, 0° | 27.659° / 180° | 38.451° / 177.625° | 0.284° | Inside |
| B · -33.925°, 18.424° | 29.391° / 323.57° | 52.727° / 331.915° | 0.3° | Inside |
| C · -33.869°, 151.209° | 7.414° / 347.932° | -45.553° / 226.718° | 0.079° | Inside |
Read this calculation
Polar-map radius = R(π/2 − latitude); local altitude = atan(height / horizontal separation)
This planar model places each site at its north-polar azimuthal-equidistant map coordinate. The light is directly above the selected ring latitude and longitude, at one shared height. North points toward the map centre and east follows increasing longitude. Changing the source longitude explores its daily position; the chosen astronomical time remains the shared comparison instant.
The nearby source’s apparent diameter uses the entered face-on disk diameter and slant distance. Its angular size changes as the observer’s distance changes. The sky columns show the astronomical Sun’s geometric altitude and compass direction at the same UTC instant and each site. They do not tune the nearby source separately for each row.
A cone centred downward is an explicit spotlight assumption: a site is lit when its direction falls within the half-angle. Turning off illumination can reproduce darkness at a place, but an elevated finite source still has positive geometric elevation. Compare measured direction, angular size and simultaneous visibility together.