A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Bob Goethe
Date: 2017 Jul 21, 10:40 -0700
I look forward to seeing other responses to your question, David. But one thing that comes to my mind as I think about it is from my reading of Lecky's "Wrinkles in Practical Navigation", written in 1881. He said that by definition the sun moved at precisely 15° 00.0' per hour...but that this necessarily meant that the length of a second varied over time.
In our modern case, we have defined a second as a fixed value, (slightly) independent of the rotation of the earth...and so the movement of the sun seems to be not quite right.
One can either have a fixed length second, and the movement of the sun can appear to vary, or you can define the sun's movement to be completely regular, and end up with a second of variable length. You cannot have both.