A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Mike Freeman
Date: 2019 Dec 22, 00:10 -0800
Seasons greetings to you also.
It seems there are sufficient methods of creating a plotting sheet to be able to use a different method on each day of the year if you wish.
I happen to have thousands of pieces of A4 paper clean on one side. I do not have a printer to print plotting sheets off the internet, in fact I have never seen a plotting sheet. I am just learning Celestial Navigation (at home) and it suits me to construct a plotting sheet using what I have to hand, although I would like to think the method is bona fide.
The method of drawing a diagonal at the degrees of latitude, creating a right triangle then measuring the hypotenuse does seem to provide the correct Lat/Long ratio.
I realise with the Mary Blewitt method it is irrelevant whether the latitude scale, longitude scale or in fact the diagonal is marked first as long as a line is scribed with a set of dividers from the diagonal to the latitude scale and a vertical line dropped from the diagonal to the longitude scale. Either this provides the correct ratio between lat and long or it does not. 1 on the lat scale = 1 on the long scale whether degrees or minutes. The Mary Blewitt method relies on it and so does yours.
There is one thing about your method I am having difficulty with (penny has not dropped).Movement of the observer. Perhaps you could provide additional explanation.