From: "Roger W. Sinnott" <[EMAIL PROTECTED]>
For example, I have several English almanacs for the year 1714. One of them
is The Ladies Diary: or, the Woman's ALMANACK. Next to many dates
throughout the year, it has phrases such as:
"Watches 3 minutes, 49 seconds too fast"
"Watches have gained of the Sun 2 minutes in 8 days"
"Watches will be 14 min. slower than a good Sun-dial"
Dear Roger,
That is fascinating indeed!
Now, I appreciate that your point is/was that, in those days, sundial time
was considered the "correct" time; but, I come at this from a different
direction. I wonder if you will please re-post those discrepancies, as
noted above, but with the DATES appropriate to the discrepancies,
or corrections. I ask this because I am interested in knowing whether the
Equation of Time (EOT) was calculated at all correctly, back then. To probe
that,
we must know the dates for which the corrections pertained.
Nowadays, I do not use the tabulated EOT corrections which appear in the
usual sundial reference books, but I calculate them afresh, using the
(low-) precision formula on page C2 of THE ASTRONOMICAL ALMANAC.
The authors claim that the formula is good to about three seconds.
I find this useful for the rectification of Equatorial and Polar
standard-time
dials I've designed.
If we had the dates for the corrections you've posted (or, perhaps, many
more
such examples, please!), we could check the arithmetic of the compilers of
that
almanac (or, more likely, of their sources...), and perhaps discover some
details
of the algorithm they used, and the values assumed by them(or known to them)
for various astronomical quantities. Could be a fascinating little study...
.
Thank you so much for posting.
--Joe Montani / Tucson, AZ
Another one, John Wing's Almanack, says on the cover that it contains "an
Equation Table, for the rectifying Pendulum Clocks and Watches."
(Unfortunately, that particular table is missing from my copy.)
-- Roger
Alas... can this be expeditiously reproduced by finding a copy (library?)
elsewhere? --Joe
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