/ 
Astro-Coords-0.03
River stage one • 4 direct dependents • 5 total dependents
/ Astro::Coords::Fixed

NAME

Astro::Coords::Fixed - Manipulate coordinates that are fixed on the sky

SYNOPSIS

  $c = new Astro::Coords::Fixed( az => 180,
                                 el => 45,
				 units => 'degrees');

  $c = new Astro::Coords::Fixed( ha => '02:30:00.0',
				 dec => '45:30:03',
				 units => 'sexagesimal',
				 tel => $telescope,
			       );

DESCRIPTION

This subclass of Astro::Coords allows for the manipulation of coordinates that are fixed on the sky. Sometimes a telescope should be commanded to go to a fixed location (eg for a calibration) and this class puts those coordinates (Azimuth and elevation for telescopes such as JCMT and Gemini and Hour Angle and Declination for equatorial telescopes such as UKIRT) on the same footing as astronomical coordinates.

Note that Azimuth and elevation do not require the telescope latitude whereas Hour Angle and declination does.

METHODS

Constructor

new

Constructor. Recognizes hash keys "ha", "dec" and "az", "el".

$c = new Astro::Coords::Fixed( az => 35, el => 30 );

$c = new Astro::Coords::Fixed( ha => $ha, dec => $dec, tel => $tel);

Usually called via Astro::Coords rather than directly.

Note that the declination is equivalent to "Apparent Dec" used elsewhere in these classes.

Azimuth and Elevation is the internal format. Currently there is no caching (so there is always overhead converting to apparent RA and Dec) since there is no cache flushing when the telescope is changed.

Accessor Methods

_azel

Return azimuth and elevation (in radians)

($az, $el) = $c->_azel;

Can also be used to store the azimuth and elevation (in radians).

$c->_azel( $az, $el);

General Methods

type

Returns the generic type associated with the coordinate system. For this class the answer is always "FIXED".

This is used to aid construction of summary tables when using mixed coordinates.

stringify

Returns a string representation of the object. Returns Azimth and Elevation in degrees.

array

Array summarizing the object. Retuns Return back 11 element array with first 3 elements being the coordinate type (FIXED) and the az/el coordinates (radians).

This method returns a standardised set of elements across all types of coordinates.

ha

Get the hour angle for the currently stored LST. Default units are in radians.

$ha = $c->ha;
$ha = $c->ha( format => "deg" );
_apparent

Return the apparent RA and Dec (in radians) for the current time [note that the apparent declination is fixed and the apparent RA changes].

If no telescope is present the equator is used.

_hadec

Return the Hour angle and apparent declination (in radians). If no telescope is present the equator is used.

($ha, $dec) = $c->_hadec;

NOTES

Usually called via Astro::Coords.

REQUIREMENTS

Astro::SLA is used for all internal astrometric calculations.

AUTHOR

Tim Jenness <t.jenness@jach.hawaii.edu>

COPYRIGHT

Copyright (C) 2001-2002 Particle Physics and Astronomy Research Council. All Rights Reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.