A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Bruce J. Pennino
Date: 2021 Mar 14, 12:02 -0700
This thought has been fermenting? with too much in-house Covid time. It is all related to reading something many times but not fully thinking about it. I was looking in Mixter's Primer of Navigation ( 5 th Edition) for something, and I renoticed Figure 1611, pg 199. This shows Capt Sumer's first plot. I realized that the tiny dot on the figure was his DR position (tiny print & old eyes). His DR seems amazingly good, +/- 10 nm, even considering his years of experience and math ability. He had not done a sight for several days. At 7-8 knots,that amounts to 500-600 nm. Wow! Even assuming he has made this trip before in this ship, there are so many factors which would greatly influence his position. Currents, good and not so good helmsmen, compass accuracy, waves, currents ,etc. are so variable. This is mighty good dead reckoning. He was so confident that he did his time sight varying only 10 minutes each time. Fortunately the LOP went right through Small's Light. Based on examinging ship's logs, is this dead reckoning especially skillful , or was he a bit fortunate? Of course,any LOP would have been helpful.
Best regards to all.