True night starts when sun 18 degrees below horizon
— EarthSky (@earthskyscience) June 24, 2016
Latest twilight 40 degrees N. tonight:https://t.co/RwSkfxurgj http://pic.twitter.com/srlxhoztkv
via Twitter https://twitter.com/earthskyscience
June 24, 2016 at 10:37PM
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