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    Re: Chuck's Lunar
    From: Arthur Pearson
    Date: 2002 Mar 22, 13:11 -0500


    It is invaluable to have a circle of colleagues with whom to compare notes. I have put Chuck's lunar into my spreadsheet using the average watch time, Ds, and time-adjusted altitudes as listed by Bruce below. With the benefit of comparing my results to Bruce's, I was able to find several gross errors in my spreadsheet.  Once corrected, I came up with a GMT for the time of observation of 00:18:15, March 19. This is 35 in advance of Bruce.

    My intermediate results were as follows:

    Sa:   7* 5.'7

    Ma:  44* 29.'7

    Moons R&P:   38.'45

    Venus R&P:   7.'28

    Moons Augmented SD:   15.'18

    D, the cleared distance: 38* 43.'2

    The only material difference in our approach I am aware of is that I am using augmented SD of the moon to reduce the sextant altitude of the moon (Ms) to Ma.  Parallax and refraction of the moon seems to be the largest area of intermediate discrepancy, I may need to examine my formulas in that area and follow the flow of Bruce's tables again to find other differences.  All in all, I am happy to be in the ball park. It is extraordinary how sensitive this technique is to very small differences in measurement or method of reduction.

    Clear skies in Boston, I will try to get a series of observations today to share with the group.



    ----Original Message Follows----
    From: Bruce Stark
    Reply-To: Navigation Mailing List
    Subject: Re: Chuck's Lunar
    Date: Fri, 22 Mar 2002 11:13:14 EST
    The values I got were:
    Average watch time of observation: 00:15:29
    Ds, average sextant distance: 37� 43.2.
    Reduced to that time, Venus above horizon: 7� 8.'7.
    Moon's lower limb above horizon: 44� 17.'6.
    From table 1, adjustments for dip and semidiameter were -3.'1 and +11.'9 for
    Venus and the moon, respectively.
    Sa, apparent altitude of Venus: 7� 5.'6.
    Ma, apparent altitude of moon's center: 44� 29.'5.
    From table 2, moon's refraction and parallax: 38.'32.
    From table 3, Venus' refraction and parallax: 7.'21.
    From table 4, moon's augmented semidiameter: 15.'17.
    D, the cleared distance: 38� 42.'9.
    D1, distance at 00 hours: 38� 34.'8.
    D2, distance at 01 hour: 39� 2.'3.
    GMT per observation: 00:17:40, March 19th.
    You may get slightly different average values by graphing than I get by
    arithmetic. For proportioning, if you use a calculator to proportion the
    altitudes to the average time of the distances, and to find the GMT that fits
    the distance, you should get the same degree of accuracy I get with tables 7
    and 8.
    It's quite possible I've made a mistake somewhere. I double check as I go
    along, but still make mistakes sometimes.
    More after breakfast.

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