Re: [LEAPSECS] new delta-T data point
In message <20171103173224.ga10...@ucolick.org>, Steve Allen writes: >I'm a bit disturbed by the plotted path of that eclipse because it is >very wide and includes the entire Nile delta as well as modern >Palestine, Israel, Jordan, and Baghdad at sunset. Unless weather >prevented it, somebody else should have made a record of that eclipse. And they probably did, but it didn't survive or we havnt torn down the city built on top of it later. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] new delta-T data point
On Mon 2017-10-30T16:23:57-0700 Tom Van Baak hath writ: > In the news... > > https://academic.oup.com/astrogeo/article/58/5/5.39/4159289/Solar-eclipse-of-1207-BC-helps-to-date > ( https://academic.oup.com/astrogeo/article-pdf/58/5/5.39/20098470/atx178.pdf > ) Alas for Delta T on date -1206 October 30, that annular eclipse moves almost entirely along a parallel of latitude, so Delta T pretty much only affects the endpoint where the eclipse happened at sunset. I'm a bit disturbed by the plotted path of that eclipse because it is very wide and includes the entire Nile delta as well as modern Palestine, Israel, Jordan, and Baghdad at sunset. Unless weather prevented it, somebody else should have made a record of that eclipse. -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] new delta-T data point
On 2017-10-30 16:23, Tom Van Baak wrote: https://academic.oup.com/astrogeo/article/58/5/5.39/4159289/Solar-eclipse-of-1207-BC-helps-to-date ( https://academic.oup.com/astrogeo/article-pdf/58/5/5.39/20098470/atx178.pdf ) "To facilitate the calculations we adopted the latest solution for the historical variations in the Earth’s rotation (Stephenson et al. 2016)..." Relevant to UTC are the tables of historic LOD (length of day) values and extrapolations into the future. In 2100 the predicted LOD is 1 ms. In 2200 it's 3 ms, same as at the dawn of the leap second era. (However, the error estimate is ±3 ms.) Earth Rotation - the Change in the Length of Day and ΔT http://astro.ukho.gov.uk/nao/lvm/ ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
