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Henry H, you wrote:
"The calculation time to complete this work, exclusive of observation time,
but including the Longitude work-up was 22-minutes - and I'm a bit rusty.
Claims that this problem required hours to solve are simply myths."

Yep. And frequently-repeated! It's in Sadler's book. It's in the PBS/Nova
documentary about longitude. And it's in Sobel. As I noted before, they're
all getting this number, very likely, from an article published in the
Transactions of the Royal Society (THE science journal of its era) which
reported 3 to 4 hour computation times in the days before the Nautical
Almanac was first published. Those folks spent hours because they had to
calculate the Moon's true position every time. That's a lot of work!

"When I get the opportunity, it is my intent to publish these observations
on the List. However, as the accuracy of Longitude obtained is really
astounding, I am double checking everything before giving George and Frank a
go at it."

Have you tried running it up using the clearing tool on my web site here:
http://www.HistoricalAtlas.com/lunars ?
Click on the link there that says "Clear a Lunar Online". It does the
standard spherical triangle solution and includes a couple of minor details
like refractional flattening and the oblateness of the Earth (neither of
these usually make a lot of difference and you can de-select them if you
want to see whether they're significant in a particular case). The almanac
data is tabulated in advance, for the entire preiod from 1750 to 2050, so
you don't need to input that. You can also download predicted lunar distance
tables for any day in that period if you wish.

You say that the resulting longitude accuracy is "astounding". I frequently
find the same thing, and I have seen interested beginners get amazing
results, too. Alex often gets annoyed when I say that beginners can get good
results, so it occurs to me that I should qualify this statement from now on
by noting that these are often people with excellent technical observing
skills in other fields. I don't grab people off the street and say, "hey
kid, wanna find yer longitude?" :-) They come to me with a natural interest
in arcane technical arts like navigation. They're often people with skill in
amateur astronomy or photography, for example. The sorts of people who can
align things through an eyepiece in any technical field can pick up a
sextant for the first time and get an excellent longitude right off the bat.
My own standard deviation for measured lunar distances is about 0.2 minutes
of arc so that's about +/-6 minutes in longitude. Not infrequently, the
error is simply zero (less than 1.5 minutes of longitude to be more
specific).

 -FER

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