NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: M.O.O. Alternative table 1
From: Russell Sher
Date: 2001 Nov 28, 2:47 AM
From: Russell Sher
Date: 2001 Nov 28, 2:47 AM
Hi Eric - welcome to the list... As far as the Alternative table 1 goes, I don't know of any gain in using this for small boat navigation where (relative) ground speeds are minimal. The tables were of course designed with aviators in mind. I have never heard of (or read of) any emphasis on using them for marine navigation. As far as your second question goes; Remember that the tables are simply precomputed formulae.(where Hc and Zn are computed using Dr Lat, LHA and DEC as arguments) Volume 1 simply exploits the fact that the declinations of stars change very little and so technically, there may be a slight loss of accuracy here between extremes of a year. However there is the correctional table supplied for this purpose. Also, by dividing Volume 1 into north and south hemispheres the table will of course give azimuth Zn, directly (as opposed to azimuth angle Z which must be converted.) But in any case Ho249 is not as accurate as Ho229 - note that in Ho249 the azimuth angles and calculated altitudes do not give decimal point precision. For small-boat navigation this is quite acceptable. This should further suggest that there is not much gain in using Alt table 1. (perhaps other opinions will prevail...!) Volume 1 also forms a star identifier/locator by precomputing the Hc and Zn of the body. ********************************************************************** Notice: The information contained in this e-mail (including any attachments) may contain commercially sensitive or confidential information which may be legally privileged and is for the sole use of the intended recipient(s). If you are not, or believe you may not be, the intended recipient, you are hereby notified that any use, dissemination, copying, review, disclosure or action taken in reliance of this e-mail is prohibited and may be unlawful. If you have received this message in error, please notify the sender immediately by reply e-mail and delete all copies of the message. Any views expressed in this message are those of the individual sender unless expressly stated by the sender to be given on behalf of Tellumat (Pty) Ltd. Tellumat (Pty) Ltd disclaims liability for any unauthorised opinion or representation made by the sender on behalf of Tellumat (Pty) Ltd. No warranty is given by Tellumat (Pty) Ltd that the integrity or security of this e-mail (including any attachments) has been maintained through transmission, nor that the communication is free of virus, interception or interference. **********************************************************************