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On Dec 10, 2004, at 1:31 AM, Frank Reed wrote:

>
> Fred, you wrote:
> "The only one that's somewhat serious is Nov 14, 1778, and that's out
> by
> 25" of arc.  This can't explain discrepancies of 1 degree of arc!"
>
> Maybe I should have mentioned that I simply picked a few dates totally
> at random, to give a taste for the sorts of discrepancies you might
> find... some days very close, other days significantly out of line,
> and I should add with no periodicity (which would be easy to correct).
>
> Here's what Maskelyne has to say about the matter in the preface to
> the Nautical Almanac that year:
> "These new tables [...] seem to give always the Moon's longitude in
> the Heavens correctly within 45 seconds of a degree; which greatest
> error, added to the possible error of one minute in taking the Moon's
> distance from the Sun or a star at sea, will at a medium produce an
> error of 50 minutes of longitude".

Frank,

I believe one would need to check the almanac inaccuracies for each of
Thompson's lunars to confirm that they were a significant part of his
1-degree discrepancies.  At this point, it does not appear that they
account for much of the variation.

Regarding those inaccuracies, it would be helpful to see the entire
series of observations for each of the lunars.

Fred

   

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