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Michael Wescott wrote:


> In practice, this is practical on ships and even small boats. Joshua Slocum
> (the first around alone sailor) seems to have preferred Lunars to keeping his
> Chronometer on time. The drawbacks are in the difficulties involved with taking
> three "simultaneous" sights (two altitudes and the angle between them) and in
> the calculations involved to reduce the sights.

Actually, you don't need to shoot the altitudes. They are only used to provide
corrections for reducing the angle between. You can use calculated altitudes and
work back to the apparent altitudes, which then provides you with corrections you
need to reduce the sight.

In addition to making the sight easier, it opens the use of lunar distances to
situations where you have no horizon available. The Navigation Foundation's
newsletter had a series of stories about Lewis and Clark using this method.

As Russell Sher already mentioned, if you want to actually practice these methods,
check out Bruce Stark's book, "Tables for Clearing the Lunar Distance." It has
everything you need to do lunar distance sight reductions with a current nautical
almanac. The process may seem a little tedious at first, but just like doing
intercept method sight reduction, it gets easier with practice.

--
Carl Herzog

   

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