Astro:...:Fixed(3pm)

💫 Astro::Coords::Fixed — the "just point there and stay there" coordinates ✨

Hey bestie, welcome to the perl manual page for Astro::Coords::Fixed, straight out of the User Contributed Perl Documentation (that's the 3pm section, iykyk). Let's get into it 🫶

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🎀 NAME 🎀

Astro::Coords::Fixed — literally the class for manipulating coordinates that are fixed on the sky. No drifting, no drama, just vibes pinned in place 💅

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✨ 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,
                               );

Look at her go 😭 two whole construction styles, both iconic.

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🌸 DESCRIPTION 🌸

Okay so this is a subclass of Astro::Coords, and what it does is let you manipulate coordinates that are fixed on the sky. Sometimes a telescope should just be commanded to go to a fixed location — like, for a calibration, bestie — and this class puts those coordinates on the same footing as astronomical coordinates. We're talking Azimuth and elevation for telescopes like JCMT and Gemini, and Hour Angle and Declination for equatorial telescopes like UKIRT. All equal, all valid, periodt 👑

Heads up: Azimuth and elevation do not require the telescope latitude, but Hour Angle and declination do. That's not a suggestion, that's just how it is 🙈

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🔥 METHODS 🔥

🧚 Constructor

new — the constructor, obviously. Recognizes the 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. You can call it directly, but like... why would you 💀
• 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 — because there's no cache flushing when the telescope is changed. Not a bug, just a fact 🍓
• A telescope is required (in the form of an "Astro::Telescope" object) if the position is specified as HA/Dec. No telescope, no HA/Dec, no exceptions ✋
• A reference to a 2-element array can be given to specify different units for the two coordinates, e.g. "['hours', 'degrees']". Cute and flexible 💖
• A name can be associated with this position. She has a name, use it 🎀

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🌈 Accessor Methods

azel — return azimuth and elevation (as two "Astro::Coords::Angle" objects):

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

Can also be used to store the azimuth and elevation (as "Astro::Coords::Angle" objects):

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

Yes, that's the underscore version for setting. Sneaky but iconic 💅

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⭐ General Methods

type — returns the generic type associated with the coordinate system. For this class the answer is always "FIXED". No cap, always.

This is used to aid construction of summary tables when using mixed coordinates. Team player energy 🫶

stringify — returns a string representation of the object. Returns Azimuth and Elevation in degrees.

summary — return a one line summary of the coordinates. In the future will accept arguments to control output. (Future, bestie. Not yet. 🙈)

      $summary = $c->summary();

array — array summarizing the object. Returns back an 11 element array with the 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. Consistency is her love language ✨

ha — get the hour angle for the currently stored LST. By default returns format as for other angular methods.

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

apparent — return the apparent RA and Dec (as two "Astro::Coords::Angle" objects) for the current time. Note that the apparent declination is fixed but the apparent RA changes — she's fixed, she's not frozen 😌

If no telescope is present the equator is used.

hadec — return the Hour angle and apparent declination (as two "Astro::Coords::Angle" objects). If no telescope is present the equator is used.

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

ha_set — for a fixed source, the setting Hour Angle has no meaning. That's it, that's the whole method. It's giving "not applicable" energy 💀

meridian_time — meridian time is not defined for a fixed source. Nope. Not a thing.

transit_el — transit elevation is not defined for a fixed source. Always returns undef. Always. Every single time 🙈

apply_offset — overrided method to prevent "Astro::Coords::apply_offset" being called on this subclass. Do not pass go, do not apply offset 🚫

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🦋 NOTES 🦋

Usually called via "Astro::Coords". Like, that's the normal way, bestie.

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💜 REQUIREMENTS 💜

"Astro::PAL" is used for all internal astrometric calculations. All the math, all the heavy lifting, she outsources it 🔥

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👑 AUTHOR 👑

Tim Jenness <tjenness@cpan.org>

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🌸 COPYRIGHT 🌸

Copyright (C) 2001-2005 Particle Physics and Astronomy Research Council. All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA

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Fr fr, that license text stays exactly as-is, we don't play with legal wording 💅

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okay that's the whole page bestie, you're officially fluent in fixed coordinates 🌈✨

Signed, sealed, delivered by perl v5.42.2, dated 2026-02-15, and stamped Astro:...:Fixed(3pm) — muah, slay 🎀💋