A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Homer Smith
Date: 2023 May 14, 13:27 -0700
I live in SLC, UT (111.811W, 40.726N) and west of me, a little bit to the north, is the Great Salt Lake (GSL). Over the past few years as I have been learning about CN, I have wondered if I am far enough away from the lake for it to be a true horizon. An island and mountains make up the background. I find from Google Maps that they are 34+ statute miles away from me provided that I am looking at least 12 degrees to the north of due west. Any closer to due west, the surface of the lake is obscured by elevated evaporation ponds. Rounding to the nearest ft, the elevation of the lake is 4193 ft, the elevation of the balcony that I will be taking my sightings from is 4958 ft and the distance from my eye to the surface I am standing on is 5 ft, making my HOE = 770 ft. Taking the sq rt of (770 X 1.5) gives me a distant to the horizon of 33.98 statute miles. It appears to me that I do have a true horizon for the part of the lake that I can see. Have I figured correctly? Is the distance to the horizon valid for such a large HOE? If I brought a CB down to this horizon with my sextant, are there altitude correction tables that I can look up dip and refraction for this HOE? Is there anything else that I need to take into consideration (besides I.C.)? Does it make any sense to use this distant horizon? If the lighting is just right I can see a fairly distinct horizon, but not as distinct as it would be from 3 miles away.
My level of interest is that of a land-based navigator that has taken most of Frank's CN classes.