The Big Dipper

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Have you ever noticed that some photos show so many stars that it's hard to pick out the constellations? The Big Dipper -- actually an asterism, or smaller figure, within the larger constellation of Ursa Major -- is thought to be the most widely-recognized star pattern (it has been given many different names around the world, including the "Plough" in Europe). But you may have trouble immediately identifying it in this photo, partly because it is standing on its "handle" shortly after rising above the northeast horizon. Position your mouse cursor over the image to show the Big Dipper and the names of its component stars.

The stars of the Big Dipper are actually members of a large open cluster that is relatively near to us. Among them are Merak and Dubhe, the last two stars in the "bowl" of the dipper -- they are the so-called "pointer stars," because they form a celestial signpost directing us to the nearby North Star, Polaris. Also notable is the star at the bend in the "handle," which is actually a pair that forms a natural eye chart -- skywatchers with good vision can not only see the bright star Mizar, but also its close dimmer companion, Alcor.

Date: November 18, 2006
Time: 11:37 p.m. MST
Location: Four Peaks Road, Arizona
Camera: Olympus OM-1 35mm SLR on homemade tracking mount
Film: Fuji Sensia 400 slide (pushed one stop)
Focal length: 100 mm
Aperture: f/2.8
Exposure time: 4 minutes
Scanner: Nikon Coolscan LS-2000