A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2015 Mar 8, 20:07 -0400
I enjoyed your article and purchased one of these units off of eBay.
I've been thinking about that (up to) 5° shift in the latitude for the azimuthal equidistant overlays.
Consider a 10° latitude. We can move the 5° overlay up to 10° or the 15° latitude down to 10°. But now consider, the 5° and the 15° overlays have unique shapes so there must be some error associated with either when used at 10° latitude.
In order to determine this, I may have to resurrect the 2102e, so a mathematical result can be obtained.
Alternatively, one could pull out two sequential overlays to the 2102d and directly observe the error.
I wonder if your research had led you down this path?
Marine navigators have used the 2102-D star finder for many years as an aid to planning sights or identifying stars. The U.S. Air Force developed a variation in the mid-1950s called the CP-300/U that incorporated a number of useful enhancements.
I wrote this article some years back for the “The Navigator’s Newsletter” History of Navigation column (Issue #77 Fall 2002 pp.6-12) but no one seemes to have ever heard of this device or know what it fate was. Perhaps someone here has additional information.
(CP-300-U-for-frn-blog.pdf: Open and save or View online)