Guiding Lights

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	Guiding Lights

Subject: Circumpolar Stars Date: June 25, 1998 Location: Rio Rancho, NM Lens: 50mm F-stop: 1.7 Exposure time: 7 min Filters: none Film: Kodak Max ISO/ASA: 800 About the Title: The center star is Polaris, or the North Star, which remains in the same place throughout the course of the night and from night to night. For years, travelers have counted on its constancy to show them the way, to guide them. Back to Astrophotos		This seven-minute exposure shows the diurnal motion of the stars. Because of the Earth's rotation, the stars seem to circle in the sky throughout the night. They make one complete revolution in 23 hours 56 minutes. The camera was aimed roughly at the North Celestial Pole. Because the Earth's axis points in thisdirection, Polaris and the stars near it do not seem to move at all,whereas the stars farther away move quickly, evident by thelonger paths of the stars toward the edges of the picture. Note thatthe sky is blue even in the middle of the night. See also Magestic Trails