Talk:Astronomical coordinate systems

message: This is a nice comparison article. May I suggest adding the Zodiac Coordinate system — used by Ptolemy and other ancient astronomers — to the table. It uses the ecliptic as it fundamental plane, the ecliptic poles as its poles but in contrast with the ecliptic coordinate system it uses stars (Antares and Aldebaran) as its fixed frame of reference and therefore requires no epoch. Actually, I believe there are two separate zodiac coordinate systems. One sidereal system using the fixed stars and requiring no epoch and one tropical zodiac using an epoch fixed to the vernal equinox around the time and Hipparchus. It's a useful coordinate system for those with very few modern day instruments. 41.248.252.130 (talk) 21:20, 11 May 2008 (UTC)
thread_title:  Zodiac Coordinate System 

message: The suggestion of a zodiac celestial coordinate system also raises the issue of the prime meridian for the coordinate system. It might be worth having another column in the table for that too. 41.248.252.130 (talk) 22:40, 11 May 2008 (UTC)
thread_title:  Prime Meridian 

message: It seems to me that the title should be plural, "Celestial coordinate systems", since the article refers to several.  --George100 (talk) 12:00, 7 June 2008 (UTC)
replies: text: I think singular is in accord with the article naming policy, we don't have birds except as a redirect to "bird", we have bird, irrespective of how many there are. An article Celestial coordinate systems should just be a redirect, but for editors it isn't needed since the link Celestial coordinate system could just be followed by an "s" and the link will just look perfect! ... said: Rursus (mbork³) 14:04, 18 November 2009 (UTC)
thread_title: Plural title?

message: How can the coordinates of an object remain constant? Due to the earth's rotation, don't they change with time?  —Preceding unsigned comment added by 122.169.1.73 (talk) 17:16, 24 March 2009 (UTC)
thread_title: Change with time

message: The article needs some explanations to purpose of respective coordinate system. Altazimutal is for the momentaneous observer on earth at a certain time. If a sailor measured up a star or planet position at a certain time and compared to his planetary tables, longitude and latitude on earth could be computed. Equatorial is for the astronomical observer. He/she generally has instruments adjusted to equatorial positioning of astro-objects. Ecliptical positioning is for Astrology, a practically obsolete usage, or, less obsolete, for a lot of solar system metrics. Galactic positioning is for interstellar astronomy that regards object distribution in the galaxy — that we could guess from the name! Extragalactic positioning is for whatfor, whatever or something else, that surpasses my knowledge... ... said: Rursus (mbork³) 14:12, 18 November 2009 (UTC)
replies: text: Did so μself. ... said: Rursus (mbork³) 14:52, 18 November 2009 (UTC)
thread_title: Some explanation needed

message: I tried to duplicate the illustration "Orientation of Astronomical Coordinates" in 3D with AutoCAD and I get an error, particularly that the earth north pole is tilted toward the center of the ecliptic in December, away from the center of the ecliptic in June, which seems wrong to me. So I question whether the autumnal equinox and vernal equinox are labeled correctly, or whether something else I am interpreting from this illustration is incorrect.
Did this illustration come from some source that I can verify?
Where can I verify the 98 degrees and the 123 degrees?
Betweendust (talk) 18:29, 25 November 2011 (UTC)
replies: text: I think the image is mostly correct (although I confess it required a bit of thinking on my part).  The vernal equinox in the image is not the location of the Earth on the vernal equinox, but rather the location of the sun on the celestial sphere at that time of year.  The placement of Earth in the diagram is confusing (and potentially wrong).  The 98 and 123 degrees I can't verify without more careful calculation but it seems about right magnitude (angular distance between NCP and NEP comes out to ~23.5 degrees). Is that helpful?  The diagram is a wikipedian's own work (not my own) so I can't read their mind for how the digram was made. Sailsbystars (talk) 22:33, 25 November 2011 (UTC)
thread_title:  Request source of the illustration "Orientation of Astronomical Coordinates" 

message: Isn't the Earth the Center of any "Celestial Coordinate System"?
:As such shouldn't the Celestial Sphere be Concentric with the Earth's surface
:The diagram show's the Sun's orbital center as the center of the "Celestial Sphere"
This diagram is confusing to me, and seems inconsistent with this and other pages on Astronomical Coordinate Systems
Daccadprose (talk) 23:50, 13 January 2012 (UTC)
replies: text: There are at least three different origins of coordinates, the Earth, the Sun, and the Galactic center, and on the Earth there are the local rotating system (usually the topocentric one), the barycenter, and the center of some ellipsoidal reference frame (WGS84 and siblings). R. J. Mathar (talk) 10:19, 4 October 2012 (UTC)
thread_title:  Origin of Coordinate Systems 

message: The table in the section Celestial_coordinate_system#Coordinate_systems now has "horizontal" and "vertical" coordinates listed. Since these are all angles on a sphere, there is no horizontal or vertical. Vertical is the direction in which gravity pulls when you are standing on a planet. Yes, if you turn the celestial sphere around into some certain contrived orientation, you could then say, perhaps, that latitude is like vertical, but in the real sky nothing is oriented that way. The horizontal coordinate system, which is based where the observer is standing, is the exception. We can write it to explain all of this, if that's what we want. Tfr000 (talk) 14:24, 16 May 2015 (UTC)
replies: text: Fixed it. Tfr000 (talk) 16:00, 4 July 2015 (UTC)
thread_title:  Table is a little odd now 

message: Maybe I'm as thick as a brick, but the explanation of the vernal equinox as the origin of longitudinal position is not clear. I think it needs a little clarification. In which direction would I be facing on the vernal equinox in order to face the origin? I understand where the Earth is located relative to its orbit around the sun on the vernal equinox, but that seems to be a location in space (the point where the Earth is located on the vernal equinox), not a direction or a line. Is the origin a line from the Earth through the sun on the equinox? If so, is the zero point where the sun is located in the sky, or is it along that same line facing the zenith at solar midnight? It seems there is one element missing still. We have the Earth's location relative to the sun at a given time, but how do we derive direction from that? The ecliptic plane and the celestial plane intersect along a line between the Earth and sun, ok, but which direction along that line is the origin of longitudinal position? (I think I'm repeating myself.) Dcs002 (talk) 23:24, 4 June 2016 (UTC)
thread_title:  Vernal equinox 

message: :The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this section. 
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:Celestial coordinate system →  – The authoritative IAU's resolutions recognize only two types of celestial reference systems: barycentric and geocentric; also notice the proposed article title was merged into the present article in the past. fgnievinski (talk) 05:46, 25 May 2021 (UTC)
replies: text: Why not provide a citation to the authoritative IAU resolutions? Jc3s5h (talk) 02:51, 31 May 2021 (UTC)
replies: text: Sorry, here it is: IAU (2000), Resolution B1.3: Definition of barycentric celestial reference system and geocentric celestial reference system fgnievinski (talk) 00:54, 6 June 2021 (UTC)

text: Support the PLURAL exception “Articles on groups or classes of specific things”.  The article covers the multiple coordinate systems, not the general concept which is quite trivial and is covered by the first paragraph. SmokeyJoe (talk) 09:58, 14 July 2021 (UTC)

text: Agreed with plural, as in the skew coordinates example given in WP:PLURAL#Exceptions. fgnievinski (talk) 23:38, 14 July 2021 (UTC)
thread_title:  Requested move 25 May 2021