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Hi all,

Concerning the errors that Slocum would have discovered, let me add
this.

An article appeared in the 'Navigation'  journal (Vol. 44 no. 1, 1997)
in which the author (S.Y. van der Werff) discusses lunar distances and
particularly the lunar distance observation of Joshua Slocum on june
16, 1896, shortly before his landfall on Nukahiva. He comes up with a
completely different kind of error that Slocum discovered and
corrected.

Van der Werff notes that the Nautical Alamanc uses the astronomical
date convention, i.e., a new day begins at noon, not at midnight. The
layout of the lunar distance tables is such that one can not be
mistaken by 12 hours, but not so the right ascension and declination
tables. Van der Werff's suggestion is that Slocum accidentally took
the RA/Dec values for a time 12 hours off (12 h too late, actually).
Slocum's 'discovery', then, was that the tables were 12 hours off.

If that was indeed the error that Slocum made, I conclude that he was
_very_ unfamiliar with the time convention in the almanac. He would
have had no earlier occasion to stumble over this difference of 12
hours, or at least no such occasion had occured in the voyage with
'Spray' and for quite some time before. It would imply that usually he
took from the almanac only data that were forgiving of such an error:
declinations, but no right ascensions. I would conclude that, on the
large, Slocum's only means of astronomical navigation was by meridian
altitudes.

Does this appear as a likely scenario to list members?

Steven.

PS I will be away until after christmas.

-----------------------------------------------------------
Steven Wepster                          wepster@math.uu.nl
                                        tel +31 30 253 1531
Mathematisch Instituut                      +31 61 251 4380
Universiteit Utrecht
PO Box 80.010
3508 TA Utrecht
The Netherlands
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