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    Re: Lunars with SNO-T
    From: Alexandre Eremenko
    Date: 2004 Oct 28, 13:14 -0500

    Dear George,
    I am surprised that that one rejected distance in
    my first lunar triggered so much exchange.
    I think this is based on some misunderstandings,
    and maybe my statements in this exchange were not clear
    enough.
    
    Let me begin with two statements which I want to make
    completely clear:
    
    1. What does it exactly mean: "rejected an observation".
    I did not erase it from my log. When necessary I reduced it
    too and the result is kept in my log.
    I rejected it IN COMPUTING THE AVERAGE.
    The purpose of computing and reducing the average is to
    obtain the "final result", let's say, my chronometer correction.
    I want my chronometer correction to be as close to the TRUTH
    as possible. Could I make any use of this "rejected" distance?
    Yes, I could. When I would judge about the likely error
    of my observations, I WOULD take it into account.
    But to compute my chronometer correction I decided to reject it.
    The later reduction of rejected distance PROVED that
    for this particular series I was right:
    rejecting this observation improved the average.
    
    2. In my explanation why I rejected it, I did not mean to
    formulate any general rules for rejection.
    I rejected it using my common
    sense.
    And then, when asked, tried to analyse and explain how my
    common sense worked in this particular case.
    If I am asked to state a general rule for rejection, the
    only rule would be:
    USE YOUR COMMON SENSE.
    
    Now let me comment some points of your message.
    On Wed, 27 Oct 2004, George Huxtable wrote:
    
    > I ask him if he can quote any authority in support
    > of such a dogmatic attitude.
    
    The only authority is my common sense.
    I repeat this is not a dogmatic attitude:-)
    The statement was nor a "rule", not a "dogma", but
    an attempt to explain how my common sense worked in this
    particular case.
    
    > Pursuing this matter, I have asked whether the rejected point in his first
    > lunar set would still have been rejected if the discrepancy had been an
    > arc-minute less-
    
    Such questions can be asked to infinity:-)
    When my son was 4 years old I told him that the highest
    mountain is Everest. His next question was: "What is the lowest mountain?"
    I tried to explain him why this question has no reasonable
    answer. Do you really want me to repeat this explanation
    on this list?
    
    > That shows a welcome flexibility creeping in, but the picture I get is that
    > Alex is very reluctant to abandon his self-imposed rule.
    
    I repeat: the only "self imposed rule" was:
    use common sense. (This rule I will never abandon:-)
    Again: I never wanted to claim that EVERY deviation from monotonicity
    has to be rejected in EVERY set of data.
    And sorry if my statements could be interpreted like this.
    I was talking of THIS PARTICULAR series, nothing else.
    
    A question to George:
    Suppose you are in Sea, have no radio, and taking lunars
    to compute your chronometer correction.
    And you obtained exactly that series of lunar distances I had.
    How would you proceed? Would you average all 6 or reject one?
    
    > Finally, I asked Alex this question about his second set of lunars-.
    
    > be interesting to know exactly what were those averaged values that were
    > fed back into Frank Reed's program, and whether any rounding had taken
    > place.
    
    Those averaged values were given in my observation reports: In the first
    report: AVERAGE GMT: 4:13:13 AVERAGE DIST: 23.54' In the second report:
    AVERAGE GMT: 0:26:28
    AVERAGE DIST: 70d41.0'
    
    They were rounded to 1 sec of time and .1' of distance.
    Which I always do, of course: if the almanac itself does it,
    what is the point of messing with extra digits myself?
    
    > So there's no
    > discredit to Frank's program.
    
    Who was talking on "discredit"???
    Of course, his program also does rounding, how else can it be??!
    
    Alex.
    
    
    

       
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