Astro::Coord::Precession - Precess coordinates between 2 epochs
Version 0.02
use Astro::Coord::Precession qw/precess precess_rad read_coordinates/; # If you have coordinates in float RA hours and Dec degrees: my $precessed = precess([$RA, $dec], $epoch_from, $epoch_to); # If you have coordinates in rad: my $precessed_rad = precess([$RA_rad, $dec_rad], $epoch_from, $epoch_to); # If you have coordinates in strings with RA h,m,s and Dec deg etc: my $coord = read_coordinates(['01 33 50.904', '+30 39 35.79']); my $precessed = precess($coord, 2000, 2021.15);
A very simple, pure Perl module to precess equatorial coordinates from one epoch to another, based on the algorithm P. Herget used in the Publications of the Cincinnati Observatory.
my $precessed = precess($coord, $epoch_from, $epoch_to);
Returns an arrayref [$RA, $dec] with equatorial coordinates (0 <= RA < 24 in hours, -90 <= Dec <= 90 in degrees), precessed from $epoch_from (e.g. 2000) to $epoch_to.
[$RA, $dec]
$epoch_from
$epoch_to
$coord input is similarly arrayref with RA in hours, Dec in degrees.
$coord
my $precessed_rad = precess($coord, $epoch_from, $epoch_to);
Returns an arrayref [$RA, $dec] with equatorial coordinates in rad, precessed from $epoch_from (e.g. 2000) to $epoch_to.
The precess function converts from/to rad anyway, so use this if you can work with rad directly.
my $coord = read_coordinates([$ra_string, $dec_string]);
Returns coordinates in an arrayref of RA, dec in decimal values to use with precess. It accepts commonly used strings for RA, dec in hours and degrees respectivelly:
$ra_string
It will read a string with hours, minutes, secs like '2 30 00' or '2h30m30s' or '02:30:30' etc. Single/double quotes and single/double prime symbols are accepted for denoting minute, second in place of a single space/tab which also works. Will accept negative too with preceding -, even though this is unusual and also no seconds part.
'2 30 00'
'2h30m30s'
'02:30:30'
$dec_string
It will read a string with degrees, minutes, secs like '+54 30 00' or '54°30m30s' etc. Single/double quotes and single/double prime symbols are accepted for denoting minute, second in place of a single space/tab which also works. Will also accept no arc seconds part.
'+54 30 00'
'54°30m30s'
Dimitrios Kechagias, <dkechag at cpan.org>
<dkechag at cpan.org>
Please report any bugs or feature requests to bug-astro-coord-precession at rt.cpan.org, or through the web interface at https://rt.cpan.org/NoAuth/ReportBug.html?Queue=Astro-Coord-Precession. You could also raise issues or submit PRs to the github repo below.
bug-astro-coord-precession at rt.cpan.org
https://github.com/dkechag/Astro-Coord-Precession
Based on the precession function from the fortran program CONFND, made by FO @ CDS (francois@simbad.u-strasbg.fr).
This software is copyright (c) 2021 by Dimitrios Kechagias.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
To install Astro::Coord::Precession, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Astro::Coord::Precession
CPAN shell
perl -MCPAN -e shell install Astro::Coord::Precession
For more information on module installation, please visit the detailed CPAN module installation guide.