NavList:

Robin Stuart, you wrote:
"Finally it was pointed out that by 1916 time sights were obsolete and had been replaced by intercept-azimuth LoP’s."

This was incorrect. This opinion tends to arise when armchair historians consult navigation manuals and textbooks and assume that they describe actual practice. Navigation textbooks are not the same as navigation practice. Of course textbooks do not represent practice, except in rare cases. Worsley's navigational method was quite normal in this period of time, and a large portion, maybe even a majority, of practicing navigators at sea continued to use time sights, not even extended to Sumner lines, as their normal, primary method of working up a longitude from a sight well into the 1940s. Why? Maybe because it works?

If you want to understand navigation history, like any other form of history, you have to look at primary source materials. Imagine if the history of science or the history of mathematics were constructed by reading and interpreting only published articles in journals. That approach yields a cartoon of history where article A leads directly to article B which leads then to article C. How comforting such histories are with the warts of reality erased and expunged. It's all so linear...

Time sights lasted for decades after they're killed off in the cartoon histories. And Sumner lines were a footnote for decades after Charles Sumner's initial publication. And lunars were nearly dead 50-60 years before they disappeared from the exams and textbooks and almanacs. Real history is more complicated. And I should add that the history of celestial navigation is also cultural with different practices applied by different subsets of navigators.

I suspect that many modern navigators have difficulty understanding the twisting strands of the history of our subject because of the static, nearly frozen practices that exist today, at least as exemplified by the licensing exams.

Frank Reed