|Sunrise(3pm)||User Contributed Perl Documentation||Sunrise(3pm)|
NAME¶DateTime::Astro::Sunrise - Perl DateTime extension for computing the sunrise/sunset on a given day
use DateTime; use DateTime::Astro::Sunrise; my $dt = DateTime->new( year => 2000, month => 6, day => 20, );
my $sunrise = DateTime::Astro::Sunrise ->new('-118','33',undef,1);
my ($tmp_rise, $tmp_set) = $sunrise->sunrise($dt);
DESCRIPTION¶This module will return a DateTime Object for sunrise and sunset for a given day.
- my $sunrise = DateTime::Astro::Sunrise -new(longitutide,latatude,ALT,Iteration);>
Eastern longitude is entered as a positive number Western longitude is entered as a negative number Northern latitude is entered as a positive number Southern latitude is entered as a negative number
There are a number of sun altitides to chose from. The default is -0.833 because this is what most countries use. Feel free to specify it if you need to. Here is the list of values to specify altitude (ALT) with:
- 0 degrees
- Center of Sun's disk touches a mathematical horizon
- -0.25 degrees
- Sun's upper limb touches a mathematical horizon
- -0.583 degrees
- Center of Sun's disk touches the horizon; atmospheric refraction accounted for
- -0.833 degrees
- Sun's supper limb touches the horizon; atmospheric refraction accounted for
- -6 degrees
- Civil twilight (one can no longer read outside without artificial illumination)
- -12 degrees
- Nautical twilight (navigation using a sea horizon no longer possible)
- -15 degrees
- Amateur astronomical twilight (the sky is dark enough for most astronomical observations)
- -18 degrees
- Astronomical twilight (the sky is completely dark)
- Notes on Iteration
a) Compute sunrise or sunset as always, with one exception: to convert LHA from degrees to hours, divide by 15.04107 instead of 15.0 (this accounts for the difference between the solar day and the sidereal day.
b) Re-do the computation but compute the Sun's RA and Decl, and also GMST0, for the moment of sunrise or sunset last computed.
c) Iterate b) until the computed sunrise or sunset no longer changes significantly. Usually 2 iterations are enough, in rare cases 3 or 4 iterations may be needed.
($sunrise, $sunset) = $sunrise->($dt);¶Returns two DateTime objects sunrise and sunset. Please note that the time zone for these objects is set to UTC. So don't forget to set your timezone!!
AUTHOR¶Ron Hill email@example.com
- Paul Schlyer, Stockholm, Sweden
- for his excellent web page on the subject.
- Rich Bowen (firstname.lastname@example.org)
- for suggestions
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.