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I agree with George's comments.

I have a couple of additional points:

First is a minor one.  I didn't like this statement:

  At that moment, anyone on the surface of the earth who can see the
  same two bodies will observe the same angle (after correcting for
  errors).

Strictly speaking, the only significant "errors" are sextant and
reading errors, and the mariner has no way of "correcting" those.
Aside from that, the lunar distance observed by the mariner differs
from what would be seen by the imaginary observer at the center of a
transparent earth because of parallax and refraction.  However, I'm
uncomfortable calling one of those observations more "erroneous" than
the other.  They are observations of different things.

My first thought was to change the parenthetical statement to "(after
corrections)", but I still didn't like it.  The only way two people
will both "observe" the angle listed in the almanac is if they are
both at the center of the earth, and *not* "on the surface".

One could say "(after adjustments)", but it would still be wrong - the
people at different places are not actually "observing" the same
angle, they are *calculating* the same angle.  At that point I decided
the sentence had too many problems and deleted it.  However, I didn't
record any rationale on the "discussions" page, and it was restored.

Could we agree to something like this:

  At that moment, anyone on the surface of the earth who can see the
  same two bodies can observe that angle and determine what time it
  is.



My second point concerns the "method" discussion. A couple of versions
ago, it ended this way:

  Knowing Greenwich time and local time, the navigator can work out
  longitude.

I changed that to

  Knowing Greenwich time and the altitudes of the moon and the other
  body, the navigator can apply the [[intercept method]] to find his
  latitude and longitude.  Alternately, the navigator can [[longitude by
  chronometer|first determine local time, and then longitude]].

At present, it says

  Having found the time, and having the altitude of a star as well as
  the Moon, the navigator can now use the techniques of [[Celestial
  Navigation]] to find the vessel's position at the time of the
  observation.[1]

I don't mind removing the reference to the intercept method, which
came later.  However, the current link to Celestial_navigation has the
same problem.  That page actually starts by showing two circular lines
of position derived from two altitude measurements.  But mariners
could not do that calculation until the intercept method was invented!

My reference to [[longitude by chronometer]] was really to the concept
that knowing the (Greenwich) time and one altitude lets you calculate
the longitude. A chronometer is one source of the time. The lunar is
another source of time. That's why I changed the wording of the
reference, so what the reader sees is "first determine local time, and
then longitude".

So, if there is only one cross-reference, I think [[longitude by
chronometer]] is more appropriate than [[celestial navigation]].

(By the way, I still think the "longitude by chronometer" page needs
some work.)

             - Jim Van Zandt

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