Re: Off Topic: average daylight

From: Gerhard HOLTKAMP (grd.holtkamp@t-online.de)
Date: Fri Jun 16 2006 - 15:18:32 EDT

  • Next message: Jeff Umbarger: "Re: Off Topic: average daylight"

    A few months ago (having had nothing better to do at the time) I calculated 
    the total hours of sunshine and various twilights for different latitudes in 
    2005. The Northern Arctic Circle came out first with sunshine hours (4647 h). 
    The North Pole had 4575 h, the equator 4422 h, the Southern Arctic Circle 
    4530 h and the South Pole 4387 h. (Sunshine being defined as the upper limb 
    of the sun still visible with refraction.)
    
    The maximum of civil twilight hours (the center of the sun being higher than 
    -6 degrees) was at 69 deg north with 5513 h (and not at the artic circle with 
    5487 h). The North Pole showed 5212 h, the equator 4684 h and the South Pole 
    5031 h. 
    
    If it comes to the total hours of perfectly dark sky (sun below -18 deg and no 
    moon) the worst was 80 deg North with just 801 h (the North Pole had 829 h). 
    You could enjoy 1788 h at the equator and 1066 h at the South Pole. (Of 
    course your total darkness at the poles would further get disturbed by 
    aurorae!) 
    
    Ironically, although the equator is best for dark skies it seems to be less 
    favorable for visual observations of low flying satellites due to the short 
    twilight there and also due to the fact that polar orbiting satellites are 
    converging over the polar regions and can be observed more frequently there. 
    So pick your favorite satellite observation spot!
    
    Gerhard HOLTKAMP
    Darmstadt, Germany
    
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