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    Re: Lunar trouble, need help
    From: George Huxtable
    Date: 2008 Jun 15, 00:17 +0100

    I've been looking at Kent Nordstrom's Lunar distance calculation, without 
    recalculating his results..
    
    What Jeremy measured was the angle between the near limbs of the Sun and the 
    Moon.
    
    What is predicted in the Lunar Distance table in the Almanac is the angle 
    between their centres.
    
    Somewhere, then, there should be a step in the calculation in which the 
    semidiameters of Sun and Moon should be added to the observed lunar 
    distance. I can't see that step shown explicitly. However it might be 
    included within Kent's "old fashioned way" of reducing the lunar distance. 
    If not, it should be in there somewhere.
    
    George.
    
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ----- Original Message ----- 
    From: "KENT AE NORDSTR�M" 
    To: 
    Sent: Saturday, June 14, 2008 7:46 PM
    Subject: [NavList 5451] Re: Lunar trouble, need help
    
    
    
    Jeremy asks for help.
    
    I don�t know if I can help but certainly provide some comments.
    
    
    
    The normalized values from Jeremy�s series of observations should be:
    
    -         mean LD 86 d 10 m 18 s (same as Jeremy)
    
    -         mean time for LD observation should be 06-22-59 (what type of
    time??)
    
    -         the altitude for the sun to 06-22-59 should be 33d 07,43m
    
    -         the altitude for the moon to 06-22-59 should be 61d 19,3m
    
    After reduction of altitudes and distance (my old fashioned way) is
    obtained:
    
    -         moon 61d 20m 52,6s
    
    -         sun 33d 11m 43,57s
    
    -         distance 86d 14m 45,64s
    
    
    
    At GMT 0600 the true distance is 85d 31m 59s
    
    At GMT 0900 the true distance is 87d 01m 05s
    
    At GMT 1200 the true distance is 88d 29m 50s
    
    
    
    Consequently the measured truse distance is between 0600 and 0900.
    
    
    
    The GMT for the measured true distance (incl. The correction for account of
    second differencies) is 07-26-17,74.
    
    
    
    Regards
    
    Kent N
    
    ----- Original Message ----- 
    From: "Anabasis" 
    To: "NavList" 
    Sent: Friday, June 13, 2008 10:15 AM
    Subject: [NavList 5413] Lunar trouble, need help
    
    
    
    I am having a bit of trouble with a lunar I shot this week at sea.
    It was late afternoon and I tried for a more �traditional� lunar.  I
    shot an altitude of the sun, then the moon, then 5 lunar distances,
    followed by another sun and finally another moon altitude.  (in
    retrospect, I should have shot the 2nd moon first then finally the
    second sun)
    
    My first trouble was with the moon altitudes.  The Hs of the sun was
    nearly 2x and on opposite bearings as the moon so I was getting
    massive flashes of the sun where it hit my horizon mirror and bounced
    back through the scope.  I have a feeling that my altitudes of the
    moon are none too accurate.
    
    Here is my data around 0620 on 10 June 2008.
    
    1) Sun LL: Hs 33deg 58.5� @ 06h 19m 13s UTC
    2) Moon UL:  60deg 36.8� @ 06h 20m 44s
    3) LD1: 86deg 10.3� @ 06h 21m 40s
    4) LD2: 86deg 10.0� @06h 22m 20s
    5) LD3: 86deg 10.2� @06h 22m 52s
    6) LD4: 86deg 10.6� @06h 23m 24s
    7) LD5: 86deg 10.6� @06h 24m 39s
    8) Sun LL: 32deg 35.8� @ 06h 25m 19s
    9) Moon UL: 61deg 49.2� @ 06h 26m 28s
    
    DR (didn�t take a fix) Latitude was 15deg 14.0�N and Longitude was
    144-04�E.  Ship was on course 270 at 12.0 knots.  IE was 0.0 T/P was
    98deg F and 1010MB.  Height of eye is 106 feet.
    
    I averaged the two sun lines to get 33deg 17.2� at 06h 22m 15s, then
    the two moon altitudes to get 61deg 13.0� at 06h 23m 37s.  Finally the
    5 LD�s averaged to 86deg 10.34� at 06h 22m 59s.
    
    I had trouble when I used Frank�s online calculator where I input the
    three mean sight numbers and used the mean LD time.  Then I used the
    near limbs I got an error of over 35� of arc.  This looked an awful
    lot like the two semi-diameters added together, so I substituted far
    limb for near and got a LD error of 0.9� which seems more reasonable.
    Something is amiss, and I don�t know enough about shooting lunars to
    know what is going on.  Can anyone help me out here?
    
    Jeremy
    
    
    
    
    
    
    
    
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