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Kent Nordtrom has provided useful comments on his methods, in explaining-

"So again, what I have tried to achieve is a re-construction of how the LD�s
were measured and reduced in the old days (by Swedish navigators) and not
necessarily what will be achieved with todays know-how."

Indeed, that explains a lot about the differences between Kent's procedures 
and my own.  His aim, in authentically following the path set by 
19th-century Swedish navigators, is of great interest to me, and no doubt to 
others as well. I wish him success, and hope that he will publish his 
findings (in English).

He adds-

"Also keeping the local time with a watch was used but after what I have
gathered this was not a common method likely because watches were not good
enough. But this method, when working, was certainly much easier for the
navigator than the first method outlined by me."

Well, there are big differences between the timekeeping standard required 
from a watch that's expected to keep home-port time over the duration of a 
voyage (which needs to be some sort of chronometer), and a watch that's just 
used to relate times of observations, taken within a day or so (a 
deck-watch). With a deck-watch, you can use a lunar to check its error, and 
then use that to note a separate time-sight taken at a different 
time-of-day, so the whole job doesn't have to be done at once. Such 
deck-watches were available at sea for ordinary mariners, long before 
chronometers were.

There's little to be found, in English-language texts, relating to Swedish 
ocean navigation. There's a perception, true or false, that in the 19th 
century the Swedes were great traders with other North-European nations, in 
timber and minerals, but mainly confined within the Baltic; and that, 
presumably, wouldn't call for lunar-distance navigation.. That may relate to 
Sweden's lack of overseas colonies to exploit. Certainly, in the previous 
century, Sweden, with af Chapman, had been very advanced in ship design, and 
in Stockholm precise angle-instruments were being made by Ekstrom and 
others. I hope that Kent can some time tell us a bit more about 19th century 
marine technology, in Scandinavia.

I will address the differences that have shown up, in the detail, between 
Kent's analysis of Jeremy's lunar, and mine, in another posting.

George.

contact George Huxtable at george@huxtable.u-net.com
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. 


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