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    March 29 Lunar
    From: Arthur Pearson
    Date: 2002 Mar 30, 21:09 -0500

    Ladies and Gentlemen:
    
    I had another humbling night with the sextant on Friday.  I measured the
    distance between Regulus and the far limb (east facing).  This on the
    night of the full moon when the moon was more than 180� of GHA east of
    the sun, so I think I was working with a fully illuminated limb.  While
    I had some blurriness of the limb while making some of the contacts, I
    felt reasonably confident.  You can see from the results that I still
    had some scatter (+ - 1.0�), but taken together I got a reasonably
    consistent set of sights for a beginner (ie, all sights were within 1.0'
    of the best fit line).
    
    Unfortunately, the bottom line was less pleasing. My distance yielded an
    estimate of GMT 5 minutes 27 seconds ahead of GMT by GPS. Using Bruce's
    method for translating that error in time to error in distance measured,
    I was long by 3.4'. I went back out and reexamined a star-moon contact
    and moved my arc back and forth 3.4', and it is a glaringly obvious
    difference, I would not have missed it in taking the sights. So I begin
    to suspect instrument error or some other systematic error. I worked the
    calculations by two different methods, so I don't think they are the
    problem, but would love it if they were.  I am curious if the full moon
    in any way distorted my limb, but I think that is wishful thinking.
    Please let me know if any of you find an explanation for this error.
    More practice....
    
    Time and position by GPS
    Date:   3/29/02
    Time            Ds
    02:22:22        44� 19.8
    02:25:16        44� 22.6
    02:26:26        44� 21.8
    02:28:02        44� 23.9
    02:29:15        44� 23.0
    02:30:37        44� 24.8
    02:31:40        44� 23.8
    02:33:03        44� 25.0
    02:34:06        44� 25.5
    02:35:18        44� 25.0
    02:36:16        44� 26.4
    
    DR Lat          42      22.7    N
    DR Lon          71      9.9     W
    Selected Time   2       30      0
    I C                             -2.6    min
    
    Body:   Regulus
    GHA1            216�    18.3
    GHA2            231�    20.8
    Dec1            11�     57.4    N
    Dec2            11�     57.4    N
    SHA Star        207�    52.6
    SD Sun          0
    
    Body:   Moon
    GHA1            22�     47
    GHA2            37�     14.9
    Dec1            0�      44.2    S
    Dec2            1�      0.1     S
    HP Moon         61.3    min
    
    D1              43�     1.1
    D2              43�     39.0
    Delta / hr              37.9
    Sc              59�     34.5
    Sa              59�     35.1
    Mc              33�     5.4
    Ma              32�     15.0
    Moon R&P                50.41
    S R&P                   -0.59
    Moon aSD                16.86
    Ds              44�     24.0    at far limb
    Da              44�     4.5
    D               43�     23.5
    GMT Obs 2:35:27
    Dist Err                3.4'
    
    More practice, more practice...
    
    Regards,
    Arthur
    
    
    

       
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