NavList:

I've been doing some experimentation with marine sextant observations near where I live, at the north end of the Chesapeake Bay, where we don't have sea horizons as we normally think of them -- the line between water and sky.  It got me thinking about the geometry, and the math involved in depression of the horizon (dip) corrections, so I wrote up a tech note on (possibly) usable horizons or horizon substitutes in confined waterways, in particular the Chesapeake Bay, for practice sextant observations.   The note is at https://gkaplan.us/content/Chesapeake_Sextant_Obs.pdf and I'd be interested in any comments. I've sent it to an instructor I know at the Naval Academy.  Has anybody else either thought about this general problem, know of any other relevant references, or better yet, had any experience doing these kinds of observations? (I only have a plastic sextant and am not very good at using it, so my observations are not good enough to verify, or falsify, my development.)

- George Kaplan