Talk:September equinox

Equinox on September 21

This equinox will occur on September 21, 2096 in UTC and so the changre just made by an anonymous editor is justified. Karl (talk) 12:08, 20 August 2014 (UTC)

2015 sep Equinox: 2015-Sep-23 08:20:33.876

It is very difficult to find the exact times of solstices and equinoxes, to better than a minute of resolution -- and therefore hard to resolve discrepancies in various sources.

• stellafane.org/misc/equinox.html

This source has a handy any-year calculator that gives

TDT = Wed, 23 Sep 2015 08:21:33 GMT

UTC = Wed, 23 Sep 2015 08:20:06 GMT

but the footnotes explain that these times are only approximate, to about a minute of accuracy (and the following shows them to be about a half-min off).

• www.survival.org.au/solstice2013.php

This is the best discussion of how hard it is to obtain exact times, and how to get them from an online NASA calculator:

• ssd.jpl.nasa.gov/horizons.cgi

Ephemeris Type [change] :  	OBSERVER
Target Body [change] :  	Sun [Sol] [10]
Observer Location [change] :  	Geocentric [500]
Time Span [change] :  	Start=2015-09-23 08:20:30, Stop=2015-09-23 08:20:40, Intervals=20
Table Settings [change] :  	QUANTITIES=30,31
Display/Output [change] :  	default (formatted HTML)
2015-Sep-23 08:20:33.000        68.182392 179.9999901   0.0002366
2015-Sep-23 08:20:33.500        68.182392 179.9999957   0.0002366
2015-Sep-23 08:20:34.000        68.182392 180.0000014   0.0002366
2015-Sep-23 08:20:34.500        68.182392 180.0000071   0.0002366
Date__(UT)__HR:MN:SC.fff            CT-UT    ObsEcLon    ObsEcLat

Which leads to:

2015-Sep-23 08:20:32.876        68.182392 179.9999887   0.0002366
2015-Sep-23 08:20:33.876        68.182392 180.0000000   0.0002366
2015-Sep-23 08:20:34.876        68.182392 180.0000113   0.0002366
The dynamical Coordinate Time scale is used internally. It is equivalent to the current IAU definition of "TDB".

Giving a final result of:

2015-Sep-23 08:20:33.876 UTC (+68.182392 = CT/TDB)

In conclusion, 8:20:34 and 8:21 UTC is the proper rounded time, 8:20 is understandable -- but 8:22 seems somewhat wrong, for any general usage.-96.233.20.34 (talk) 21:37, 21 September 2015 (UTC)

Hi. I like your comment, but most of us would really appreciate an updated time for the equinox. In my view, this should be prominently displayed, and should be easy to update automatically. Curiousdale (talk) 16:57, 22 September 2023 (UTC)

more precise Solstice and Equinox times

The English speaking world seems to be limited to approximate Solstice and Equinox times, to about the nearest minute.
The French offer a more precise, to the second, master table:

• fr.wikipedia.org/wiki/Mod%C3%A8le:Solstice-%C3%A9quinoxe

2013 	20 	11:01:55 	21 	05:03:57 	22 	20:44:08 	21 	17:11:00
2014 	20 	16:57:05 	21 	10:51:14 	23 	02:29:05 	21 	23:03:01
2015 	20 	22:45:09 	21 	16:37:55 	23 	08:20:33 	22 	04:47:57
2016 	20 	04:30:11 	20 	22:34:11 	22 	14:21:07 	21 	10:44:10
2017 	20 	10:28:38 	21 	04:24:09 	22 	20:01:48 	21 	16:27:57
2018 	20 	16:15:27 	21 	10:07:18 	23 	01:54:05 	21 	22:22:44
Références :   mars • juin • sept. • déc.
Institut de mécanique céleste et de calcul des éphémérides

Most WP readers do not care about this -- but some might like access to the more accurate times. How can we provide such access in a good way? Would we ever want to replace our template master table with a more-precise master table of times? -71.174.188.32 (talk) 19:14, 22 December 2015 (UTC)

Chart

The chart is extremely hard to read. It's just a bunch of numbers all clumped together. Maybe if there are four different background shadings (one to distinguish the two columns for March; one to distinguish the two columns for June; September; December; etc.), that would make the chart easier to read. Thoughts? Thanks. Joseph A. Spadaro (talk) 19:34, 22 September 2016 (UTC)