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Dear D. Walden,

Thanks for your interesting message.
You cite my old message saying that Bennet
is apparently not good for the Lunars.

Let me make more precise what I meant.
The tables in Bennett do not have sufficient
accuracy for the Lunars, because they are
rounded to 1'. This applies both to the reduction
tables and to the almanach part.
Thus using these tables
you cannot
do better than 1' of distance in principle
(and perhaps 2' in practice, because
you need to use the tables and the almanach
several times in one
calculation
and the errors will accumulate).
Such errors in the distance in general will give you
an error of 30'-60'  in the longitude which is not
very good.
Still, if I remember correctly, even for such accuracy
a (partial) Longitude Prize was offered:-)

As I understand, in your example, the error in the true
distance was 0.6 (this is because of the rounding in
the Bennet almanac) and the error in reduction was
1'.4 (which is better than I expected).

I have one question on your calculation: when using
Frank'a calculator, why did you convert your center-to-center
distance to  the apparent
distance by subtracting 2SD? You had to subtract
(Sun SD + Moon SD) instead.

Alex.

P.S. I am also a big fan of Bennet,
especially when I have to
travel by an airplane. Then I carry a pocket sextant
(scale divided to 1') and Bennett, and nothing else.
This saves a lot of weight in my luggage, and the pocket
sextant is an ideal match for the Bennet tables.
I also use them with my bubble horizon aircraft sextant.

But when using a full size real sextant for the Lunars
I usually struggle for the tenths of a minute in the
distance, and
here Bennett is not appropriate.

Alex.


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