Talk:Epoch (astronomy)

message: Shouldn't be this defined in Terrestrial Time?
Yes, so why not change it now? Nike 06:53, 17 Dec 2004 (UTC)
thread_title: Epoch (astronomy)

message: 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)
replies: text: 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)
thread_title: question

message: Should there be a reference to Epoch/Unix time here - 1453330082 66.194.64.130 (talk) 22:48, 20 January 2016 (UTC)
thread_title: question again

message: 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)
replies: text: 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)
thread_title: #

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

text:  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)

text:  After re-reading this page on the IRCS, as well as a few other sources I came across, it seems to me that "epoch" is just a fancy word for "date". Either it refers to a date that observations were made, or the year in which an equinox occurred. So you can have an epoch of observation and an epoch of equinox. And it is totally possible that when used together they can be different. For instance, that page mentions the Hipparcos observations, which were recorded within the ICRS (which is defined by vernal equinox year 2000), but at an epoch of J1991.25 (meaning if you traveled back in time to Julian day 2448349.0625, or April 2, 1991 1:30:32 TT, all of the observations would be accurate at that exact point in time). I think this is kind of what this article is trying to say but it's not doing a very good job of it. — Elliot Winkler 08:19, 3 September 2012 (UTC)

text:  It's 1:30 p.m., not a.m. So, Julian day 2448349.0625 TT = April 2, 1991 13:30:00 TT.  — Preceding unsigned comment added by 66.65.53.212 (talk) 01:03, 16 October 2015 (UTC)
thread_title:  Epoch and Equinox 

message: 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)
thread_title:  Article is unhelpful for links from Comet Infobox 

message: 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)
replies: text: 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)
thread_title:  Julian Year 

message: We need more info about B1875. 65.94.47.63 (talk) 08:54, 2 July 2011 (UTC)
thread_title:  B1875