Homeguard, that's interesting.
I had always assumed (not sure where I got this assumption from, I guess someone must have told it to me at some point) that "the sun 12 degrees below the horizon" was some time later than official night (twilight) - around 30 minutes later.
This seemed to make sense to me. After twilight, it is still possible to see the surface of the runway, and use that (rather than the runway lights) as a visual reference for landing. Thus, it made sense to wait until some time after twilight before teaching people to fly at night, such that the only visual reference they have available is the runway lights.
But what you are saying is that this is not the case at all - that this 12-degree thing is near enough the same as twilight, but deals with the difference in appearance of the sun at altitude? In which case, my understanding of the rules has been wrong for quite some time! Oh well, it won't be the first time.....
FFF
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