A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2021 Sep 6, 18:56 -0700
Antoine Couëtte, you wrote:
"I mentioned the "folded semi-transparent sheet of paper method" to manually determine Culmination time in a series of LAN's Observation.
After some research in own Archives, unable so far to identify the Origin of this method :
- Was it published on NavList first ?
- Or was it rather published as a Navigation Paper in a Navigation Review ?"
That's my invention. Of course, like most "inventions" in this field, it has no doubt been invented before. I have written about the method in NavList messages at various times going back over a decade, and I teach it in my classes. Works great. Do you have any questions or comments about the technique?
The general concept of finding the axis of symmetry of sights around local noon and adjusting for observer motion to get longitude has been around for decades. Hewitt Schlereth wrote a nice little book based on the method (though no "folding") in the 1980s. The Admiralty Manual of Navigation discussed the mathematical details of the adjustment for motion at least as early as the 1930s. There are various ways of handling motion. It's the key detail ignored in many short discussions of the concept.