Twilight Arch
October 15, 2003
Provided and copyright by: Michiel de Boer
Summary authors & editors: Jim Foster; Michiel de Boer
The above photo was taken during the afterglow of day, last summer, in France. Clear, nearly cloudless skies were a result of the mistral (a strong, dry wind that blows down alpine slopes and into the Rhone River Valley in France). Note the twilight arch with Venus near the apex of the arch. The twilight arch is the band of light that lingers after sunset on clear nights, and it's caused by sunlight scattered by the atmosphere. Even though the Sun has set as viewed by an observer on the ground, it's still shining on the sky above. This sunlit twilight arch grows fainter and redder as twilight progresses.
The photo was made using a a 28mm objective.
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