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I will just pick out a couple of points from Jared's recent mailing, which
are those where I think I understand what he is saying.

He said-

>And what accuracy does this affect? Frankly, I can't understand why you
>say this affects >ACCURACY but not ERROR, to my way of thinking ERRORS
>cause lack of ACCURACY.

Look, Jared, say you wanted to take your own temperature, with a glass
thermometer. You could use an ordinary household thermometer, with a scale
that covered say a hundred degrees centigrade. Or you could use a special
clinical thermometer intended just for that purpose, which has a
vastly-expanded scale covering just the few degrees variation that a live
human body can possibly show. Even if both thermometers were devoid of any
errors, there's a big difference between the accuracies with which you can
measure your blood temperature. One is simply much more sensitive than the
other.

and -

>There are folks who use lasers to bounce off the retroreflectors kindly
>left by the US >Apollo program, and ham radio operators who use microwave
>transmissions and then measure >signal echo returns, so yes, the
>individual observer can measure actual lunar distance >pretty accurately
>if they own the instruments.

NO, Jared! You are confusing two quite different meanings of the term lunar
distance. What you are describing is the measurement of the distance
between the Earth and the Moon, which might well be called the "lunar
distance" in some contexts, but not in celestial navigation.

In celestial navigation the term "lunar distance" (which may not be ideal
wording, but it's become accepted) isn't used for a distance at all, but
for an angle: the angle measured obliquely in the sky between the direction
of the Moon and the direction of some other body, by an observer on Earth.

If Jared has been misunderstanding this meaning of the term "lunar
distance" in this way,  no wonder he has got confused about the whole
business!

and-

>Am I right to understand this as:
>360 degrees times 60 minutes (per degree) equals 21,600 arc minutes in one
>rotation of the earth.

Yes; that 21,600 also corresponds to the circumference of the Earth in
nautical miles.

> Equals:
>        21,600 arc minutes in 24 hours. Equals:
>                900 arc minutes per hour. Equals:
>                        15 arc minutes per minute of earth's rotation,
>i.e. GMT. Equals:
>                                1 arc minute equals 4 seconds of GMT.

OK so far-

> Equals:
>                                        .05 arc-minutes of time would be a
>two second

No, .5 minutes of arc corresponds to 2 seconds of time, and .05 seconds of
arc corresponds to 0.2 seconds of time.

George.

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