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Re: V-Correction for Sun?
From: Stan K
Date: 2016 Oct 13, 17:01 -0400

Robin,

I'll think about revealing my "proprietary algorithm" to you. I'm a little reluctant because I pretty much pulled it out of my butt.

Without it (in the "Accurate" mode), Celestial Tools pretty much always agrees with other reliable sources, like the USNO web site, which means that it will disagree with the Nautical Almanac for about 50% of the 8760 (8784) hours by as much as 0.2'. For that 1% of the "proprietary algorithm" (in the "NA" mode) that doesn't agree with the Nautical Almanac, it is only off by 0.1'.

FYI, I'm pretty sure the almost 99% number would be good for any year, but, in fact, it was only tested for 2014. With the help of a friend, we tested all 8760 hours.

I do a presentation called "Celestial Tools for the USPS/CPS JN/N Student- Its Development and Use" (with the alternate title of "How I learned more than I ever wanted to know about the Nautical Almanac". In it I show one example of the Sun GHA issue, 1 January 2015 at 00h UT. I show the results of 14 computer programs, phone/tablet apps, on-line almanacs, etc., including the USNO web site. Eleven of the fourteen, when rounded to tenths of a minute, give 179º12.2' (including the USNO site). (The other three give 179º12.1'.) The Nautical Almanac gives 179º12.0'. Celestial Tools gives 179º12.2' in the "Accurate"mode and 179º12.0' on the "NA" mode. (Sue me for picking a worst case example for the presentation.)

Stan

-----Original Message-----
From: Robin Stuart <NoReply_Stuart@navlist.net>
To: slk1000 <slk1000@aol.com>
Sent: Thu, Oct 13, 2016 3:15 pm
Subject: [NavList] Re: V-Correction for Sun?

Stan,

I'd still be interested in knowing what the algorithm is that produces the 99% agreement if you are willing to share it. How what is the percentage agreememnt without it?

Regards,

Robin

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