NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
When is the Autumnal Equinox?
From: Lu Abel
Date: 2011 Sep 3, 10:36 -0700
From: Lu Abel
Date: 2011 Sep 3, 10:36 -0700
If one goes to the US Naval Observatory web page http://aa.usno.navy.mil/data/docs/EarthSeasons.php it shows this year's Autumnal Equinox at 0905 UT on 23 September.
Whipping out my Nautical Almanac, I find that the Sun's declination is 0d 00.1m N at 0900 and 0d 00.9m S at 1000. A simple interpolation would put the Sun's declination at exactly 0d 00.0m at 0906 UT, not 0905.
Is this perhaps due to rounding in the NA data (eg, if the Sun's declination is either a tad less than 00.1' N at 0900 or a tad more than 00.9 S at 1000)??
While on the topic, does anyone know of a site that gives the equinox down to the second?? (just curious)
Lu
