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On 5 Dec 2004 at 16:29, Alexandre Eremenko wrote:

> Second, as we know from the Lewis and Clark story,
> even professional astronomers/surveyors had difficulties
> with reducing the sights.

Professional astronomers and surveyors had no difficulties with reducing
their own sights. The problems with the L&C data were not due to any
inherent problem with lunars per se.

> Only once I tried to reduce a lunar observation "by hands",
> but still using a primitive electronic calculator.
> My experience shows that this is not easy:-)

I've done quite a few lunars using only an almanac, log tables, and pencil
& paper (using old methods such as Witchell's and Maskelyne's for clearing
the distance). It usually takes me 45-60 minutes from start to finish
(including the lunar sights, but not a time sight). I have to do a lot of
double checking to eliminate errors but I think that in the days when log
tables were in common use and arithmetic calculation was heavily drilled
at school, a lunar could easily be done in 30 minutes by an experienced
navigator. Confidence in the result would come from comparing the lunar
longitude with the ded reckoning.

Not trivial but also not nearly the burden that many writers have made it
out to be. The process was entirely algorithmic for navigators. The crux
then, as it is now, was to take good measurements with the sextant.

Ken Muldrew.

   

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