NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Certificates and arc excentricity
From: Alexandre Eremenko
Date: 2007 Oct 24, 16:48 -0700
From: Alexandre Eremenko
Date: 2007 Oct 24, 16:48 -0700
In my recent message on the paper of White, I mentioned as "ridiculous" his reason for not applying the arc correction to his observations. This was so strange to me that I made a little investigation. Actually the determination of the arc correction was apparently a big problem in 1850-s. And the ordinary seamen did not know the arc correction of their sextants. Simms (of the famous Troghton and Simms) wrote several papers and a book where this is the main subject. This was in the late 1850-s. The arrangement tor measuring the arc correction was installed in the Kew observatory approximately in 1867 (not later). And perhaps from that date one could provide a sextant with a certificate. I don't know exactly when they started to issue certificates. White had a sextant (by Troughton) made "in the beginning of XIX century", so it did not have a certificate. He (White or someone else) actually determined the arc correction, and he knew it when he made his observations in 1889, but he thought that at that time an ordinary seaman would not know his arc correction. And he intentionally neglected it in his published observation. In England, you could probably bring your sextant to the Kew observatory and obtain a certificate for certain fee. Probably it was harder to do in Australia in 1889. Alex. P.S. Of course this does not remove the question how did it happen that he obtained the results within 10" of the truth if he neglected the arc correction of his sextant which was up to 20". --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---