A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Igor S.
Date: 2019 Oct 11, 01:30 -0700
1. The sun declination and procedures to determine latitude were following from the first book on celestial navigation "Arte de navegar". It has been written by Pedro de Medina ( see https://en.wikipedia.org/wiki/Pedro_de_Medina ). I have a copy of this book.
2. Whatever the instrument you mentioned, they were less precise than the tables of sun declination of that old days.
3. See the attached picture. It is aimed to use for an emergency navigation, so why not ?
The declination changes a certain amount per day depending on the month of the year. The less precise will it be when it changes fastest 0.4 deg. per day (near equinoxes) and other way around.