Talk:Epoch (astronomy)

Time Start‑class

	This article is within the scope of WikiProject Time, a collaborative effort to improve the coverage of Time on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.TimeWikipedia:WikiProject TimeTemplate:WikiProject TimeTime articles
Start	This article has been rated as Start-class on Wikipedia's content assessment scale.
???	This article has not yet received a rating on the project's importance scale.

Astronomy C‑class Mid‑importance

	Astronomy portal This article is within the scope of WikiProject Astronomy, which collaborates on articles related to Astronomy on Wikipedia.AstronomyWikipedia:WikiProject AstronomyTemplate:WikiProject AstronomyAstronomy articles
C	This article has been rated as C-class on Wikipedia's content assessment scale.
Mid	This article has been rated as Mid-importance on the project's importance scale.

Epoch (astronomy)

Shouldn't be this defined in Terrestrial Time?

Yes, so why not change it now? Nike 06:53, 17 Dec 2004 (UTC)

question

Is it known how long the current epoch will be adhered to? Do we know what will come next? Are these questions relevant; and if not, why not? Can this be clarified in the article? (As may be apparent, I don't have a clue.) -- Cimon avaro; on a pogostick. 11:58, 14 January 2006 (UTC)[reply]

Usually it's every 50 years, although I'm not certain that this is always the case. The article refers to B1875.0, which is only 25 years before B1900.0. --Nike 03:45, 16 January 2006 (UTC)[reply]

#

What's with all the #s? I've never seen this usage anywhere. #Julian epoch is just bizarre. Also, why are there links to articles which no longer exist?

Although the article only mentions one Julian epoch, I have also seen J1900 and J1950. --Nike 08:51, 3 August 2006 (UTC)[reply]

I get it, those are supposed to be links to sections within the article. You need to use a piped link. That would look like this: [[#J2000.0|J2000.0]] --Nike 09:00, 3 August 2006 (UTC)[reply]

What are Besselian vs. Julian epochs? How do they differ from each other aside from what letter is prefixed to their number? --Haruo 10:03, 6 October 2006 (UTC)[reply]

What about the article is unclear in explaining this? --Nike 11:38, 6 October 2006 (UTC)[reply]

What I want to know is why the phrase "Since the right ascension and declination of stars are constantly changing due to precession..." is repeated verbatim in every section. BIEB!! 13:07, 25 October 2006 (UTC)[reply]

My guess is that this article is actually a series of stubs that were stitched together in the hope that someone would clear the result up into some coherent whole; sadly, nobody seems to have done so yet, and the result is just a mess... - IMSoP 01:03, 5 November 2006 (UTC)[reply]

Epoch and Equinox

This page may be mis-titled completely. When speaking of terms such as 'B1950.0' and 'J2000.0', especially in the context of celestial coordinates and precession, you are speaking of EQUINOX, not EPOCH. For example, the EPOCH of observation on a star may be 1991.25, but the coordinates given for its posistion may be specified in EQUINOX J2000.0 (The Hipparcos and Tycho stellar catalogs are a good example of this). Radec 08:15, 21 January 2007 (UTC)[reply]

I found the text trying to explain the distinction between Epoch and Equinox completely confusing. MartinSpamer (talk) 12:18, 28 August 2010 (UTC)[reply]

I totally agree. I hate to be blunt but the entire section, and this entire article really, reads like a textbook. It's clearly written by someone who is an expert, but there are too many details. — Elliot Winkler 06:30, 3 September 2012 (UTC)[reply]

I found this revision which helps explain the difference between them. Well, a little bit. :/ (unfortunately nothing is referenced, so it's kind of worthless) — Elliot Winkler 06:44, 3 September 2012 (UTC)[reply]

Article is unhelpful for links from Comet Infobox

I was directed to Epoch by the Comet Infobox on the Comet McNaught article, which states "Epoch: 2454113.2961 (January 20, 2007)". It was not immediately apparent from this article that the stated epoch was in fact a Julian Day, and that I should refer to that article for an explanation of the number 2454113.2691. If a subject expert is revising this article, it would be helpful if they would consider this usage. PaulKishimoto 17:57, 21 January 2007 (UTC)[reply]

I believe this is a problem with the Comet Infobox and not this page. Icez 02:15, 5 February 2007 (UTC)[reply]

Julian Year

The article states

Julian year 2000 began on 2000 January 1 at exactly 12:00 TT.

Does that imply according to the Julian calendar? —Preceding unsigned comment added by Trigamma (talk • contribs) 22:58, 4 January 2008 (UTC)[reply]

That and other references within the article to Julian epochs are poorly worded. For J2000.0, 2000 January 1 (at noon) is in the Gregorian calendar. Other Julian epochs differ from this epoch in Julian years of 365.25 days each. Hence the Hipparchus epoch of J1991.25 is 8.75 Julian years before J2000.0. This requires significant rewording of the article. — Joe Kress (talk) 08:17, 5 January 2008 (UTC)[reply]

B1875

We need more info about B1875. 65.94.47.63 (talk) 08:54, 2 July 2011 (UTC)[reply]