Approximate model. Same simplified ionospheric engine as the grid page —
not VOACAP. The grey line and terminator are real astronomy; the colours are a model.
Reliability →
10
25
40
55
70
85
95%+
daylight (brighter = sun higher)
grey line (sun within 6° of horizon)
darkness
☉
sun overhead
●
live WSPR decode of a UK station
Reading the map