NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Bruce J. Pennino
Date: 2013 Mar 3, 15:36 -0800
Hi:
I averaged your theodolite measured dip angles and the result was 8 min 25 sec, or 8.4'. The NA gives dip = 8.3' with height of eye 22 meters. Your data looks good to me.
I'll herewith speculate that an 1800s astronomer measured dip with a telescope and produced the NA table. Possibly an equation was fitted to the measured data. This was commonly done in many technical areas. In fact, if you really delve into the most complex modern mathematical models, "coefficients" will appear. Sometimes these coefficients go back to basic lab/field work conducted 100 years ago.
Interesting and thanks. I'll go back and look at the earlier posts.
Bruce
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