NavList:

Ken M wrote:

"Yes, but it still seems odd that they would trust their dead reckoning so
much that they wouldn't update their account when they took a lunar."

 

I should make clear that they did do that sometimes. But it seems to have been done only when the evidence was overwhelming that the DR longitude was incorrect.

 

Let's imagine a simple scenario. I'm aboard a whaler on the equator in the Pacific c.1840. I take my departure from a sighting of one of the Galapagos. So I "know" that my longitude is 92..00W at that time, let's say it's noon (the beginning of the day by sea account so this is the longitude recorded in the logbook). Now I sail due west for 24 hours at 5 knots. Just before noon the next day, we shoot and work a set of lunars because there's nothing else to do and the junior officers need practice. The resulting longitude is 93..15W. That wouldn't be unusual. But by DR, my longitude should be 94..00W. Even a lunarian is likely to consider that DR lon to be a much better representation of his vessel's position than the lunar lon. That's certainly the one that would have been recorded in the logbook, perhaps with the lunar marked in the margin. And as Alex noted (and some contemporary commentators noted, too), it makes little difference what my exact longitude is unless I'm near a critical point in a voyage, like a landfall or a change of course required to make landfall.