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    Re: � � � Re: Lewis and Clark lunars: more 1803 Almanac data
    From: Ken Muldrew
    Date: 2004 Apr 22, 09:50 -0600

    On 21 Apr 2004 at 21:06, Bruce Stark wrote:
    > You may have found it, Ken.
    > You wrote: "But it's just way too close to
    > the moon; 15?, in fact. Exactly 15?. Now I can't quite figure out what
    > error would lead to the captains recording distances that were off by
    > 15?, but for some reason the fact that there are no minutes or seconds
    > in the error makes me think it's possible."
    > The vernier on Lewis's sextant read to 15" of arc, so I'm almost
    > certain the numbers on the arc would have been at 15? intervals. Also,
    > the index mark of the vernier was almost certainly near the right edge
    > of the "window frame" of the index arm. The 30? or 45? engraving they
    > should have been reading the additional degrees, minutes and seconds
    > from would have been outside the "window frame." Inside the frame,
    > where the serious reading was done, 60? would have appeared.
    I think this explanation is far more likely than my earlier thought
    that a magnitude 4.5 star was being mistaken for Aldebaran. There's a
    nice picture of just such a vernier given in the Mystic Seaport
    facsimile of Norie's Epitome. Frank Reed posted the URL about a week
    or two ago, but here's a link to the page in question:
    (that all has to be on one line).
    > Perhaps, given the difficulty of reading a vernier sextant by
    > firelight, or candle lantern, they picked up on the 60?, and counted
    > from there.
    I can believe that. Especially given the common error of using the
    wrong minute when reading their watch.
    BTW, for anyone who would like to now try reducing their sights to a
    longitude, the position of Betelgeuse at that time is:
    RA: 5h 44m 34s
    Dec: 7? 21.5'
    Just subtract 15? from all the lunar distances in George's series A
    and C.
     O_/ \    Ken Muldrew, PhD      | Voice: (403) 220-5976           |
     <\__  \  Dept. of Cell Biology | Fax:   (403) 270-0617           |
      | /
      "\ L  | University of Calgary | kmuldrew@acs.ucalgary.ca        |
    / /
       <    +-----------------------+---------------------------------+ /
                   Morning coffee recapitulate phylogeny               L/

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