view release on metacpan or  search on metacpan

lib/Astro/Montenbruck/Time/DeltaT.pm  view on Meta::CPAN

    2016 => 70.0
);

Readonly our $TAB_SINCE => 1620;
Readonly our $TAB_UNTIL => 2016;

sub _interpolate {
    my ( $jd, $ye ) = @_;

    # For a historical range from 1620 to a recent year, we interpolate from a
    # table of observed values. Outside that range we use formulae.

    # Last value in the table
    if ( $ye == $TAB_UNTIL ) {
        return $HISTORICAL{$TAB_UNTIL};
    }

    # 1620 - 20xx
    my $y0 =
      $ye % 2 == 0 ? $ye : $ye - 1;   # there are only even numbers in the table
    my $y1 = $y0 + 2;

lib/Astro/Montenbruck/Time/DeltaT.pm  view on Meta::CPAN

=back

=head1 SUBROUTINES

=head2 delta_t( $jd )

Returns approximate Delta-T in seconds for a given Julian Day.
C<Delta-T = ET - UT>

For a historical range from 1620 to recent years, we interpolate from a
table of observed values. Outside that range we use formulae from
I<Astronomical Algorithms> by I<J.Meeus>, second edition.

=head3 Arguments

=over

=item * B<$jd> — Standard Julian Date.

=back