<P> The astronomical polar night is a period of continuous night where no astronomical twilight occurs . Astronomical twilight happens when the Sun is between twelve and eighteen degrees below the horizon and astronomical night when it is lower than that . Thus, the astronomical polar night is limited to latitudes above 84 ° 34', which is exactly 18 ° within the polar circle, or five and a half degrees from the pole . During the astronomical polar night stars of the sixth magnitude, which are the dimmest stars visible to the naked eye, will be visible throughout the entire day . This happens when the sun is between 18 and 23.5 degrees below the horizon . These conditions last about 11 weeks at the poles . </P> <P> The Amundsen--Scott South Pole Station experiences this from May 15 to late July . </P> <P> The North Pole experiences this from November 14 to January 29 . </P> <P> The concept of a night of almost one month in length has been the subject of the vampire movies Frostbite and 30 Days of Night . In these films, the vampires are drawn to the long duration of darkness, allowing them to openly kill and feed at will . </P>

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