NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Bruce J. Pennino
Date: 2011 Jun 20, 11:43 -0700
I considered the same problem recently on a bluff (high dune) on Cape Cod. Most states have topo maps on-line, and you can get an elevation above MSL from the map. Close enough for a me....only a beginner and still have not purchased a sextant.
Further ,once you get above 30-40 ft, dip does not change too much per 10 ft.
Dip = 6.1' @ 40ft; 6.9'@ 50 ft; 8.7' @ 80 ft . Someday I'll worry about refinements.
Regarding free falling stone (dense object) in normal atmospheric conditions, no flutter, rotation, or any other special conditions, my calcs show
y -ft t-time sec Dip (more or less) min.
20 1.1 4.4
40 1.6 6.3
80 2.2 8.9
120 2.7 10.6
or dip is about 4 * free-fall seconds.
Bruce Pennino
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