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Dear Nigel,

I'm working on a Ph.D. thesis about Lunar Distances (LD) and Mayer's
lunar theory that made it all possible. I've experimented with lunars
this spring at sea. I prepared my own precomputed LD tables on the
model of the tables that were printed in the Nautical Almanac up to
the beginning of the 1900's. For altitude and parallax corrections etc
I used copies out of an old German almanac. And then I cheated by
doing the Clearing of the Distance on a programmable calculator...

I used LD three times to find the GMT of observation, and I could
compare the result with my quartz wristwatch. Thge results were,
approx:

1st, rather hastily: error 10 minutes (time);
2nd, error 4 minutes;
3d,  error 2 minutes.

All were under reasonably cam conditions. The fact that my boat is
only 8m long and that we were out in the Atlantic made that an
absolute necessity. For the second experiment I hove to. The third
experiment is very noteworthy, not only because it shows that a
reasonable accuracy can be obtained, but because it was done in the
middle of the night at the full moon. Undoubtly you will know the
warning about false horizons below the moon; but the  LD is not
affected by it, and the altitudes of the bodies need not be taken very
accurate. This is a rather surprising advantage of LD, I think.

Well, all this doesn't sound like an algorithm. I'll come back with
more on that later.

Yours,
_Steven


> Anyone out there with a good algorithm and process for longitude by
lunars?
>
> NG

   

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