NavList:

I live inland, and so when I take sextant sights over water, it is usually over a lake surface.  This leaves me keenly interested in knowing if the lake is wide enough, in the direction I am shooting, that I am seeing a "true horizon".  Most often when I take sights on salt water, I am surrounded by islands, and have exactly the same question I want to answer.

Bowditch 2017, of course, has table 12 that relates the height of eye to the distance of the horizon...but I never seem to have that table ready at hand.

As I was reviewing a piece of Bowditch, howeveer, I had an "Aha!" moment as I looked at these two sections that were right next to each other (screen capture attached to this post).  It had never occurred to me until this week that I could relate dip to the distance-to-horizon.  But if you have your Nautical Almanac in hand, you can get an approximation of the distance to the horizon with this, which one can do in his head:

     Dip x 1.2 = distance-to-horizon-in-nautical-miles

Bob

File: