Talk:International Celestial Reference System and its realizations

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This article is marked as "stub" but considering that it contains a link to

http://www.usno.navy.mil/USNO/astronomical-applications/astronomical-information-center/icrs-narrative

which is a perfect and complete description there is really no reason expand the article! All what should be said is said there!

Stamcose (talk) 08:08, 11 June 2011 (UTC)[reply]

Merger discussion

System and frame cannot be described without one another. fgnievinski (talk) 02:45, 2 May 2021 (UTC)[reply]

I also notice International Terrestrial Reference System and Frame. fgnievinski (talk) 22:48, 14 July 2021 (UTC)[reply]

@Mark viking: as you've undone the move, could you please comment. fgnievinski (talk) 22:48, 14 July 2021 (UTC)[reply]

That edit was was more than two years, so I don't remember the full context. But my edit summary gives the gist of it: reference system and reference frame are different concepts and I think ideally they should have separate articles. I envision the reference system article talking about the protocol or system for creating and coming to consensus on a reference frame. Then the reference frame article would talk about the history, impact and uses of the set of reference frames that have been created. How a book is manufactured and how that book is used are obviously related, but that doesn't mean that the publisher and the book should be merged into the same article.

That said, both articles are fairly short at present and a merge could be successful if both topics are clearly distinguished in the merged article. International Terrestrial Reference System and Frame is also two separate topics sitting in the same article, but it is so stubby that it doesn't make sense to split it at this point. --{{u|Mark viking}} {Talk} 00:53, 15 July 2021 (UTC)[reply]

@Mark viking: I've started Draft:International Celestial Reference System and Frame. fgnievinski (talk) 04:42, 15 July 2021 (UTC)[reply]

I also note that the official publication about the subject is titled "The International Celestial Reference System and Frame"[1] fgnievinski (talk) 04:50, 15 July 2021 (UTC)[reply]

The US Naval Observatory site is being re-organised so the links to this site including references [1], [2] & [3] are broken. Replacements for these pages do not seem to exist but may be restored when the work on the website is complete (some time in 2022). — Preceding unsigned comment added by John Murrell (talk • contribs) 10:20, 22 January 2022 (UTC)[reply]

Suggested Revisions due to Optical Reference Frames?

I recently added a discussion of the IAU's adoption of the GAIA Celestial Reference Frame for Optical wavelengths and the restriction of the use of the ICRF3 to radio wavelengths. It doesn't fit all that well in the current structure of the article. I suggest discussing the Radio and Optical Reference Frames separately. The present discussion of the various versions of the ICRF could go under a new heading of Radio Wavelengths and a new parallel discussion of the Hipparcus and Gaia reference frames would go under a new heading of Optical Wavelengths. The following outline is what I have in mind.

Versions
- Radio Wavelengths
  - ICRF1
  - ICRF2
  - ICRF3
- Optical Wavelengths
  - Hipparcos Celestial Reference Frame (HCRF)
  - Second Gaia celestial reference frame (Gaia–CRF2)
  - Third Gaia celestial reference frame (Gaia–CRF3)

Since there are now two accepted Celestial Reference Frames, I also suggest changing the title of this article to "International Celestial Reference System and Frames." Comments on these suggested changes are welcome.

--SteveMcCluskey (talk) 19:44, 10 June 2022 (UTC)[reply]

As I understand it, there is just a single ICRF3 standard based on multiband radio-wavelength VLBI observations. Gaia–CRF3 is accepted as a realization of the ICRS, but it isn't part of the ICRF3 standard, so changing the the title to "frames", where frame implicitly refers to the ICRF, would misleading. Perhaps "International Celestial Reference System and its realizations"? Implicit is in this is the subtle point While ICRS may spawn multiple reference frames, only one realization at a time is given the name ICRFn, for some value of n, and n=3 is treated as the current standard against which other realizations/frames are aligned.

An organization along the lines

Reference system and its realizations -- Briefly discuss concepts behind system, realization, and frame
- Sources -- Briefly discuss that these extragalactic sources come in multiple wavelengths, so far three radio bands and one optical band.
Versions
- Radio Wavelengths
  - ICRF1
  - ICRF2
  - ICRF3
- Optical Wavelengths
  - Hipparcos Celestial Reference Frame (HCRF)
  - Second Gaia celestial reference frame (Gaia–CRF2)
  - Third Gaia celestial reference frame (Gaia–CRF3)

may be worthwhile. That is, having an intro section would set up the context in which the optical frames could be understood as deriving from the ICRS just as the ICRFn have. I am just an amateur in these matters, however, and would be happy to be corrected if I'm misunderstanding things. -- {{u|Mark viking}} {Talk} 21:26, 10 June 2022 (UTC)[reply]