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    From: Arthur Pearson
    Date: 2003 May 18, 17:29 -0400

    It is most interesting to see the rigor with which you approach these
    observations.  I am inspired to get some additional observations this
    summer and to take a greater number in each series, as well as to take
    series of both increasing and decreasing distances.  Needless to say, I
    will share the results and look forward to seeing what I can learn about
    improved technique.
    -----Original Message-----
    From: Navigation Mailing List
    [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On Behalf Of Fred Hebard
    Sent: Sunday, May 18, 2003 4:45 PM
    Doug Royer was so kind as to post the data for his shipboard lunars of
    last week.  I looked at them, clearing each one and computing the mean
    and standard deviation of the difference in the cleared observed
    distance and the computed distance, as well as the difference between
    the known time and the time determined from the lunar.  Young's method
    for objects of known altitude was used, as outlined by George Huxtable;
    thus I ignored Doug's observations of the altitude of the bodies,
    computing them from his known position.  For comparison, I show the
    same summaries for lunars I have taken on dry land, and two that Arthur
    Pearson's took in the Caribbean aboard a small yacht.  For those who
    have difficulty reading this in a web browser, paste the table into a
    text processor and it should line up properly.
    Doug's observation are about as precise as Arthur's and mine as
    determined by the standard deviation of arc difference.  However, the
    absolute arc difference, and the corresponding time difference, is
    quite large, almost 5 minutes of arc.  Interestingly, Doug's arc
    difference goes in opposite directions for the Moon, Jupiter
    observation as compared to the Moon, Spica observation.  This leads to
    very similar time differences for the two observations.  In the Moon,
    Jupiter observation, Doug brought Jupiter to the near side of the Moon,
    but Spica needed to be brought across the face.  One possibility for
    the similarity of this discrepancy is that Doug was not bringing the
    objects all the way to the moon, but, rather, leaving a gap.
    To determine index error, I use the technique outlined by Bruce Stark,
    among others, of measuring the semi-diameter of the sun.  This
    technique might sharpen one's skills for lunars, which are measured in
    a similar fashion.
    I also have taken the liberty of including two graphs of Doug's data.
    I haven't heard any complaints yet about including small binaries like
    this.  I hope they come through.  Please let me know if they cause a
    problem, and of course, with any comments on the analysis.
                                      mean      mean      std dev   mean
    Objects              n  date     given UT  del arc'  del arc'  del time"
    Moon, Jupiter        8  12/27/02  6:36:41  0.884695  0.703781   90.26738
    Moon, Aldebaran      7  1/8/03   23:42:01  0.514089  0.830704  -62.1228
    Moon, Sun            7  1/11/03  20:33:31  1.219828  1.215593  162.5041
    Moon,Sun A. Pearson  7  1/7/03   19:42:07  1.317516  0.404807  169.1811
    Moon,Sun A. Pearson  6  1/10/03  18:37:44  1.457861  0.447954  194.242
    Moon, Jupiter        5  2/12/03   0:37:40 -0.67918   0.271337   77.6666
    Moon, Sun            6  3/9/03   20:40:13  0.981567  1.136952  129.6058
    Moon, Jupiter        5  3/10/03   3:53:50  0.693372  0.617291  -83.1301
    Moon, Sun            5  3/12/03  22:14:17  1.831421  1.846688  225.4475
    Moon, Jupiter        7  4/4/03    1:04:45  4.30333   2.602312 -524.762
    Moon, Sun            5  4/5/03   23:04:23  0.760016  0.32473   100.9633
    Moon, Jupiter        7  4/6/03    0:20:33  0.209499  0.334972  -25.5961
    Moon, Sun            8  4/6/03   18:29:38 -0.03824   0.569998   -5.04673
    Moon, Jup D. Royer   6  5/12/03   3:21:47 -5.04648   1.162142 -513.434
    Moon, Spica D. Royer 6  5/12/03   5:37:32  4.801561  0.662518 -490.445
    Moon, Jupiter, Doug Royer

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