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    Re: Lewis and Clark lunars
    From: Fred Hebard
    Date: 2004 Apr 23, 17:31 -0400

    A one-day error would come close to 15 degrees.  It also would place
    the objects at a different spot in the sky, changing refraction and
    parallax, possibly accounting for the remaining difference from the
    moon's rate of movement of about 13 degrees/day.  Do moon altitudes
    accompany the lunar distances?  These would settle this question
    On Apr 23, 2004, at 11:30 AM, George Huxtable wrote:
    > 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
    > displacement?
    > 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.
    > George.
    > ================================================================
    > 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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