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>> Frank Reed wrote-
>>
>>> From the 18th and 19th century logbooks I've studied (only a sample
>>> of the
>>> thousands out there), I've noticed a pattern. Lunars (lunar distance
>>> sights)
>>> were never a primary method of navigation for American commercial
>>> vessels.
>>> There  was no "lunars era" comparable to the "chronometer era".
>>> Rather the
>>> primary
>>> method of determining longitude until the 1830s or so was dead
>>> reckoning, as
>>> it  had been for centuries. Around 1830, the primary method began to
>>> switch
>>> over to  chronometers. During the early period of lunars, from
>>> c.1770 to
>>> c.1830, lunars  were used as an occasional check on the dead
>>> reckoning. In
>>> their
>>> logbooks,  navigators only occasionally updated their dead reckoning
>>> with
>>> results
>>> from  their lunars observations. Rather, they continued their dead
>>> reckoning
>>> until  they were able to take a new departure from a point of land
>>> with
>>> results of  lunars listed marginally. The "mindset" was centered on
>>> the dead
>>> reckoning.  After c.1830 (and it is a decades long process of
>>> transition), the
>>> primary  longitude listed in the logbooks become "long by chrono"
>>> with
>>> occasional
>>> checks  by lunars.
>>
>> and Henry Halboth added-
>>
>> "It would be of interest to consider whether all navigation
>> calculations
>> actually done aboard any particular vessel, aside from a notation of
>> position, was actually spread out on the pages of the log book, as
>> opposed to being calculated on scraps of paper or in a separate
>> workbook
>> which remained the possession of the individual."
>
> An George Huxtable added
>
> I think Henry has a worthwhile point here. Right from the earliest
> days of
> lunars, in the 1760s, printed pro-formas existed to systematise the
> calculations involved in a lunar....


Unfortunately, I expect they sailors would have said in the log:
"longitude by account," or "longitude by chronometer," or "longitude by
lunar," depending upon the method used, even if the calculations were
not recorded.

   

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