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Comment by steve_adams_86

1 year ago

They reflect sunlight for some period of the evening and morning, before the sun is shining where you are and illluminating the sky too much.

Between when the sun first disappears below the horizon and when (nearly) all its light disappears, i.e., the end of astronomical twilight when the Sun's center is 18 deg below the horizon, seems to be about 90 minutes.

https://www.timeanddate.com/astronomy/different-types-twilig...

It's been awhile, but I'm pretty sure I've seen these much later than that. I'm talking about lying in a sleeping bag, looking up at the amazing starfields of pitch-black wilderness nights (tip: never use a tent except in extremis - look what you're missing!).