NAME

Astro::Sunrise - Perl extension for computing the sunrise/sunset on a given day

SYNOPSIS

  use Astro::Sunrise;
  
  ($sunrise, $sunset) = sunrise(YYYY,MM,DD,longitude,latitude,Time Zone,DST);

DESCRIPTION

   This module will return the sunrise/sunset for a given day. 
   
   Eastern longitude is entered as a positive number
   Western longitude is entered as a negative number
   Northern latitude is entered as a positive number
   Southern latitude is entered as a negative number

   There are a number of altitides to chose from, I have chosen
   -0.833 because this is what most countries use. Feel free to 
   change it if you need to. Here is the list:
   h = 0 degrees: Center of Sun's disk touches a mathematical horizon
   h = -0.25 degrees: Sun's upper limb touches a mathematical horizon
   h = -0.583 degrees: Center of Sun's disk touches the horizon; atmospheric refraction accounted for
   h = -0.833 degrees: Sun's supper limb touches the horizon; atmospheric refraction accounted for
   h = -6 degrees: Civil twilight (one can no longer read outside without artificial illumination)
   h = -12 degrees: Nautical twilight (navigation using a sea horizon no longer possible)
   h = -15 degrees: Amateur astronomical twilight (the sky is dark enough for most astronomical observations)
   h = -18 degrees: Astronomical twilight (the sky is completely dark)

sunrise

    ($sunrise, $sunset) = sunrise(YYYY,MM,DD,longitude,latitude,Time Zone,DST);
    ($sunrise, $sunset) = sunrise( 2001, 3, 10, 17.384, 98.625, -5, 0 );

Returns the sunrise and sunset times, in HH:MM format. (Note: Time Zone is the offset from GMT and DST is daylight savings time, 1 means DST is in effect and 0 is not.

AUTHOR

Ron Hill rkhill@pacbell.net

Many thanks also go to Paul Schlyer, Stockholm, Sweden for his excellent web page on the subject.

CREDITS

Thanks very much to:

Rich Bowen (rbowen@rbowen.com)

for suggestions

Adrian Blockley [adrian.blockley@environ.wa.gov.au]

for finding a bug in the conversion to local time

COPYRIGHT and LICENSE

Here is the copyright information provided by Paul Schlyer:

Written as DAYLEN.C, 1989-08-16

Modified to SUNRISET.C, 1992-12-01

(c) Paul Schlyter, 1989, 1992

Released to the public domain by Paul Schlyter, December 1992

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

SEE ALSO

perl(1).