Southern Hemisphere Circumpolar Star Trails

June 30, 2009


Photographer: Laurent Fournet; Jean-Philippe Olive
Summary Author: Jean-Philippe Olive; Jim Foster

The photo above showing circumpolar star trails in the Southern Hemisphere was taken from Reunion Island, in the October of 2008 (austral spring). For an observer on Earth, circumpolar stars trail in a counterclockwise direction around the north celestial pole but move clockwise about the south celestial pole. Because they’re so positioned, they’re visible all night long and in fact all year long. As observed from the viewer's latitude, they never set or dip below the horizon. At the North or South Pole, all constellations that can be seen are deemed circumpolar. However, there are no circumpolar constellations at the Equator.

The Big and Little Dippers are the most well known circumpolar constellations (actually asterisms) of the Northern Hemisphere. In the Southern Hemisphere; though, there’s no bright star analogous to Polaris directly above the South Pole, several conspicuous circumpolar constellations burnish the southern sky. The two most prominent are the Southern Cross and Carina. Their striking star trails are at right center. Note: some light pollution from the city of Saint Louis contaminates the view of the night sky here.

Photo details: Olympus camera; 28mm f/8 lens; 2 hours and 40 minutes exposure time; Ektachrome 200 ASA film. Location: Les Makes Observatory 55.3° east and 21.5° south latitude; altitude 1,200 m.  Laurent Fournet and is a Jean-Philippe Olive are members of the Club Astro Astrium in Toulouse, France.

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