A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David C
Date: 2017 Jan 19, 11:37 -0800
What is particularly interesting is that although Blackburne considers the "New Navigation" a great improvement he continues to promote Sumner methods. The cynic in me says that is because he had devoted a significant proportion of his off-duty hours to calculating his tables and naturally he wanted to sell his books. Blackburne's books include many pages of testimonials from both RN and merchant navy officers. I have attached an example.
Maybe some navigators had an aversion to plotting intercepts. The advantage of the Improved Sumner Method (according to Blackburne) was that position could be determined by calculation rather than by plotting. The calculations could be done by plane trigonometry or - perhaps more importantly - by Blackburne's tables.