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    Re: Lewis and Clark lunars: more 1803 Almanac data
    From: Frank Reed CT
    Date: 2004 Apr 18, 19:30 EDT
    George H wrote:
    "Yes, apparent lunar distances sometimes CAN
    change that slowly, if the Moon gets very high in the sky: but not on that
    night at those times, as Frank's figures (and mine) confirm. Perhaps when
    the Moon approaches zenith, several hours later, its apparent speed may
    slow to correspond with observations, but that wouldn't happen until
    several hours later."

    Yes. That was really my whole point. We don't know for sure *when* they took the sights. As I noted in an earlier post, I tried to find a time later in the night that would fit the sights (since all three objects would have been up for hours after the time we think the sights were taken). It doesn't work, but at those later times at least the rate of change of the Aldebaran lunars *is* more consistent with the observations.

    And George H wrote:
    "Well, all I have here is Norton's star almanac, and I can't even hope to
    approximate such big great-circle arcs on its map projection. What it needs
    is someone with a decent-sized star-globe to see if there's some bright
    star that fills the bill; though I doubt if there is."

    Lacking a star globe, you could use a standard star chart for that night as seen from the location where the Moon's apparent position is in the zenith. Then there's no distortion of angles and the great circle arcs radiate from the zenith. There are many web sites online that can prepare a chart for this exact date and location. One that I have used is the "interactive star chart" on SkyAndTelescope.com. And no, there is no bright star that works as you already discovered.

    And wrote:
    "The original manuscript that contains this section, which is described as
    the "Eastern Journal", was discovered as recently as 1913, and is now held
    in Philadelphia, in the library of the American Philosophical Society. It
    was transcribed and edited by M.M.Quaife as "the Journals of captain
    Meriwether Lewis...", pub in 1916 by the State Historical Society of
    Wisconsin, and I have access to a copy in Oxford. It was transcribed afresh
    by Gary Moulton for his 13-volume "Journals", and I have copied data from
    Moulton into my postings to the list. And the "original manuscript" may
    well have been transcribed from rough fiel notes, made on the night. So
    there many steps in that process where errors could occur."

    Wow. That is a lot of steps. You may have taken a look at some of the ships' logbooks on the Mystic Seaport library web site. Most are scans, but some have transcriptions of the scans. There are fairly frequent errors in transcriptions despite the devotion and attention to detail of the transcribers because, of course, we're dealing with old handwritten documents. A number 2 may get transcirbed as a 9 if the original author makes the arc at the top of the 2 a little more closed. A 7 can easily be switched with a 1 and so on. A 3 can pass for an 8 if the ink is smudged. Usually though, this sort of simple transcription error stands out like a sore thumb. It's like random bit errors in digital data. They can be spotted with unsophisticated algorithms. It seems like we would need a more systematic source of error in this case...

    Frank E. Reed
    [ ] Mystic, Connecticut
    [X] Chicago, Illinois
       
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