A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Pike
Date: 2023 Mar 13, 15:20 -0700
I’ve been trying to get my head round that cones diagram, but I couldn’t work out what was wrong at first. Thank you, Frank, for answering. My clumsy argument was to have been something like this. The stars are not actually all on the surface of the same relatively small sphere. They’re all different distances of light years away. Stellar celestial calculations work because light rays arriving anywhere on Earth from a star can be considered parallel, because the star is so far away. The rays in the cone diagram are not drawn parallel. The reason the stars altitude is measured at a different angle depending upon where on the surface of the Earth you are is because the Earth is a sphere and you’re measuring altitude with respect to your local vertical.
Regarding LOP navigation, Sumner, Marc St Hilaire methods, I was simply testing to try, unsuccessfully, to find some compatibility with the spheres of GNSS. I clumsily quoted azimuths and intercepts because I was imagining manual chart, protractor, and divider plotting on a small nav-table, so you’d be looking at such a tiny segment that circles of position could be drawn as straight lines. In reality, I suppose whichever aid a modern Navy or Air Force was using, the fix would be delivered on the front of a glass screen. DaveP