NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Fw: Letcher page 103
From: George Huxtable
Date: 2010 Feb 10, 23:51 -0000
From: George Huxtable
Date: 2010 Feb 10, 23:51 -0000
--- On Wed, 2/10/10, Greg Rudzinskiwrote: > From: Greg Rudzinski > Subject: Letcher page 103 > To: hannoix@sbcglobal.net > Date: Wednesday, February 10, 2010, 10:56 AM > Hanno, > > Thanks for the forwarded web book by Letcher. Page 103 has > a most clever way to check a chronometer at sea. When doing > the Dreisonstok method I only solve for Hc then use a > standard 10" K&E slide rule to solve for azimuth using > the formula cos dec x sin meridian angle / cos Hc. =============== However, that procedure is VERY vulnerable to an error in assumed dip; particularly so, because of the use of opposite azimuths. Each arc-minute of dip error results in an error of about 4 minutes of time. George. contact George Huxtable, at george@hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.