[LEAPSECS] [Non-DoD Source] Re: new delta-T data point

Fri Nov 3 18:56:09 EDT 2017

>From the table in the reference provided by Paul Hirose's post (http://astro.ukho.gov.uk/nao/lvm/) , the uncertainty in delta-T is 0.4 hours.  At a latitude of 31 degrees, I compute a (1-sigma) distance of 500 km, which the internet tells me is about as far away as Alexandria.   Judging from the eclipse trajectory as shown, it would have required a ~ 2.5-sigma deviation to miss Canaan entirely, and another sigma of deviation to miss the Nile delta as well, although the curvature of the plot means less and less of northern Egypt would remain in the path as the visibility area moves west.   Thebes is outside of the depicted path already.   I guess their sigma is reasonable, as their figure 10 shows 180 seconds variation of Delta-T in modern times (since 1550).

But it certainly seems that if it was visible in Canaan, it should have been visible in the delta.

-----Original Message-----
From: LEAPSECS [mailto:leapsecs-bounces at leapsecond.com] On Behalf Of Poul-Henning Kamp
Sent: Friday, November 03, 2017 3:21 PM
To: Leap Second Discussion List; Steve Allen
Subject: [Non-DoD Source] Re: [LEAPSECS] new delta-T data point

--------
In message <20171103173224.GA10307 at 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
phk at FreeBSD.ORG         | TCP/IP since RFC 956
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Never attribute to malice what can adequately be explained by incompetence.
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