NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Measuring Dip in the 18th Century
From: Alexandre Eremenko
Date: 2013 Dec 28, 20:29 -0500
From: Alexandre Eremenko
Date: 2013 Dec 28, 20:29 -0500
Frank, > For the potential accuracy of backstaffs and other pre-double-reflecting > instruments, I suggested 10 minutes of arc. I want to clarify that this is > being generous. Under excellent conditions with a fine instrument and > top-notch observer, that's the best that you should expect. A reasonable > expectation for normal conditions and normal observers and instruments > would be 20-30' (in the 1 s.d. sense). How can you justify these statements? Any experiments? References? I do not mean the general common navigation errors, which can be attributed to many reasons. But any direct evidence of a backstaff performance. Alex.