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    Re: Lewis and Clark lunars
    From: George Huxtable
    Date: 2004 Apr 23, 16:30 +0100

    Ken Meldrew has been very inventive in speculating about different possible
    errors that might have been made in those Lewis and Clark lunars. And even
    considered a combination of two possible errors. I'm sure this is the right
    attitude to take. If there was an observational blunder that it was
    possible to make, you can be pretty sure that at one time or another L&C
    will have made it. There most be SOME explanation for that strange data-set
    of Dec 2-3 1803!
    His first speculation was that he had found the mystery star which had the
    right coordinates to correspond with the measured distances, supposedly to
    "Aldebaran". Already, we have established roughly how much out-of-line with
    the Moon's track (to one side or the other) a star would have to be so that
    the same star could possibly fit both sets of observations, A and C. And
    then, we have to search those two segments of sky for a star that's just
    the right distance from the Moon.
    Well, there's such a plethora of stars in the sky, that there must be many
    that will fill the bill, but the question is: is there a bright and
    prominent star, that could have been mistaken for Aldebaran? However, the
    only one Ken has been able to come up with so far is magnitude 4.5, and
    Frank Reed has pointed out that such a dim star could hardly have been seen
    in the sextant, let alone mistaken by Aldebaran, not even by L&C. I agree
    with that view, and now Kan Meldrum has acknowledged it too.
    Next Ken proposed that the sextant may somehow have been set to an angle
    exactly 15deg less than was intended. Then, as Frank has suggested, casting
    around the sky for a bright star at that wrong angle from the Moon,
    Betelgeuse would become the obvious candidate.
    But why should the sextant have been set to exactly 15deg in error for
    observation-set A? And then, set to some new value, for observation-set B,
    of "Regulus", which so far we have not considered in detail. And then set
    again exactly 15deg in error for observation-set C. This is not a single
    accidental error, it's a recurring error. What might cause the 15deg
    I thought that the answer might perhaps be found if, in error, the required
    angle had been set against the wrong end of the vernier scale, if that was
    just 15deg wide; an easy mistake to make. However, with a sextant divided
    to quarter-degrees, and a vernier reading to quarter-minutes, as this one
    seems to be, I presume that the vernier scale would be marked 0 to 15
    (minutes), but this would have to span a length on the main scale, not of 0
    to 15 (degrees) but 0 to 49 and three-quarters. Or perhaps 15 and a
    quarter; either should work. Can anyone, such as Henry Halboth, with an
    instrument calibrated to 15 arc-seconds to look at (which I don't have)
    check that this view is correct, please. If so, setting the degree scale at
    the wrong end of the vernier would give rise, not to a 15 degree error, but
    one that differs by from 15 degrees by all of 15 minutes. Quite enough to
    destroy that otherwise-attractive hypothesis, I'm afraid.
    So I am still unconvinced about the suggested scenario: that the sextant
    angle was set 15deg too small, on two separate occasions, and then
    Betelgeuse was substituted for Aldebaran. I can accept that the second
    might follow from the first, however. Can anyone offer further persuasion?
    However, I applaud the ingenuity that has been shown so far, by all
    concerned, and thank them for their continuing interest in what appears to
    be a fascinating, if intractable problem.
    Henry Halboth asks if it might be possible for the error in the lunars
    could result from measuring to the wrong limb of the Moon, and the answer
    is "no. it isn't possible". A limb blunder could give rise to an error in
    lunar distance of about 0.5 degrees, not much more. We are trying to
    explain an error of somewhat over 1deg, for obs. A, and well over 1deg for
    obs. C.
    contact George Huxtable by email at george@huxtable.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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