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All I know is that the civil twilight times are wrong for here because its always brighter for much longer... Like yesterday it was broad daylight to about 9:15 and it was twilight to about 10:15... So it is wrong...
Visible light lasts until about 12-13 deg for clear sky, even in overcast it can lasts until 8-9 deg
Visible light lasts until about 12-13 deg for clear sky, even in overcast it can lasts until 8-9 deg
For locations north of 54°34' N or south of 54°34' S latitude, the Sun will never be lower than 12 degrees below the horizon for a period in the summer.
But it doesn't get dark. Its just blue to the north and that only lasts for 30 minutes..
But you still can't walk because its dark at low level... I think probably about 57N you would have brightness all night.
Really you have to be above 60N to get a true bright night.. at local midnight (1:30am) it is pretty dark.. that picture there is taken at 12am which is not local midnight..
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