Signals lab
Daylight & gray line
Follow the boundary between day and night using a locally calculated solar position. This is a geometry model, not a propagation forecast.
Light: daylightOchre: civil twilight (0° to −6° solar elevation)Dark: Sun below −6°
An illustrative 2.5° solar grid using NOAA’s approximate solar equations and your device clock. Gray-line geometry can help explore radio paths; it does not predict reception, refraction, terrain, or ionospheric conditions. Current mode refreshes once a minute while visible; choosing a time pauses it.
NOAA solar equations ↗