#!/usr/local/bin/perl

# Display the next time the Sun reaches an arbitrary azimuth (passed in
# on the command line and defaulting to 180 degrees) from a
# pre-programmed location (Number 10 Downing Street, Westminster
# England).

use strict;
use warnings;

use Astro::Coord::ECI;
use Astro::Coord::ECI::Sun;
use Astro::Coord::ECI::Utils qw{ deg2rad rad2deg };

our $VERSION = '0.079';

my $time = time;

my $sta = Astro::Coord::ECI->new(
    name => 'Number 10 Downing Street',
)->geodetic(
    deg2rad( 51.503241 ),	# Latitude
    deg2rad( -0.127029 ),	# Longitude
    20 / 1000,			# Altitude converted to kilometers
)->universal( $time );

my $azimuth = defined $ARGV[0] ? $ARGV[0] : 180;

my $sun = Astro::Coord::ECI::Sun->new( station => $sta );

my $when = $sun->next_azimuth(
    deg2rad( $azimuth ),	# The desired azimuth.
);

print 'The ', $sun->get( 'name' ),
    " reaches azimuth $azimuth at ",
    $sta->get( 'name' ), ' at ',
    scalar gmtime $when, " (GMT)\n";

__END__

# ex: set textwidth=72 :