A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Iwancio
Date: 2020 May 13, 18:52 -0700
Correcting what I wrote earlier (because I only think of these things an hour or so after I hit "send"):
The center of the circle of equal azimuth is 5400 nmi (90°) from the observer, where the initial great-circle bearing is 090° or 270°, whichever is closer to the body observed.
The radius of the circle (analogous to zenith distance, i.e. the complement of altitude) is the body's ampllitude.