NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: determination of longitude and the prime vertical
From: Giuseppe Menga
Date: 2007 Apr 13, 09:45 +0200
From: Giuseppe Menga
Date: 2007 Apr 13, 09:45 +0200
Dear George: I checked your data with a program built by me, which is based on Swiss Ephemeris. I got the following results G.H.A 131� 9.90' decl. 15� 9.49' with a difference of 0.1' for the G.H.A. and 0.01' for the declination. We can both be satisfied of our programs! Giuseppe Menga P.S. by the way, if someone is interestes I will be happy to share my program. ----- Original Message ----- From: "George Huxtable"To: Sent: Thursday, April 12, 2007 4:45 PM Subject: [NavList 2556] Re: determination of longitude and the prime vertical > > I hope Geoffrey Kolbe's respose, with Bill's reply, show that the problems > that Bill raised in Navlist 2550 are now resolved.. > > But a minor matter cropped up in that mailing that worries me a bit. > > Bill quoted some predicted Sun positions, that had come from Andres Ruiz' > website. > > I will refer just to that first set of numbers from his mailing, as > follows- > > | Date: 1 May, 2007 > | UT: 20:41:45 > | Position: N40 W60 > | Hc: 24d 00!2 > | Az: 270.00 > | LHA: 71d 09!5 > | dec: 15d 09!5 > > I don't have a 2007 Nautical Almanac. But I have compared those numbers > with > my own predictor, held on a pocket calculator, which differs slightly. > > That gives a Sun position, at 20:41:45 GMT on 1 May 2007 of 15 deg 09.5' > N, > exactly as Bill gave it, but a GHA of 131deg 09.8', and so with a long of > 60deg W, a LHA of 71deg 09.8', just 0.3' more than the figure Bill stated. > > That difference isn't a large one, but to me it's a bit of a worry, > depending on which of us is in error. I expect the Sun predictions of that > program to be generally well within a millidegree. One might expect > divergences of 0.1', as a result of rounding errors, but not more. If my > program is out by that amount I need to investigate why. > > So I wonder if Bill will kindly recheck that figure, and ask anyone with a > current Nautical Amanac or computed equivalent, to provide a value for Sun > GHA at that moment, please. > > George. > > contact George Huxtable at george@huxtable.u-net.com > or at +44 1865 820222 (from UK, 01865 820222) > or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. > > > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---