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    Re: My first Lunar
    From: Mike Burkes
    Date: 2008 Jul 30, 13:43 -0700

     Hi folks, as usual great stuff. I have some questions. First my
    cleared distance was in agreement with you folks and my GMT yielded
    22-19-43 pretty close via Stark Tables. My 1st iteration. using
    Jeremy's DR 20N,70W yielded 17N,62W. 2nd:15 10.5N,61 51W. If the
    navigator settled on this 2nd iteration,even though short intercepts,
    I would assume this fix would be checked with a later Polaris Lat obs,
    noon sight, etc. My 3rd and final iteration yielded 14 34.5N, 61 42.2W
    pretty close to you folks' solutions. I infer the navigator would keep
    on iterating, in this case 3 times, until further iterations yielded
    agreeable results?  Thanks much.
    Mike Burkes
    
    On Jul 15, 7:03�pm, frankr...@HistoricalAtlas.net wrote:
    > Jeremy, you wrote:
    >
    > "Well I found my first lunar, and it will be tricky. �Here's the data that I
    > have.
    >
    > GMT Date is 26 January 1999. �GMT of the sight was about 2220. �Dip
    > correction is -7.7' of arc. �The lunar was at evening twilight and a near
    > limb observation between Jupiter and the Moon was taken. �The sextant LD is
    > 68deg 19.4' �IC is 0.0'. �An upper limb altitude of the moon was taken HS is
    > 66 deg 09.3' �The Hs of Jupiter is 45 deg 22.3.
    >
    > Here's the rub: �I have no idea where I was other then to say I was probably
    > somewhere in the Eastern Caribbean. �Best guess is about 20 deg North
    > Latitude and 70 degrees West Longitude."
    >
    > Having a good DR position is convenient but not necessary when it comes to
    > clearing a lunar. Of course if you want to assess the accuracy of the sight,
    > then you want the actual position and correct GMT as nearly as possible. You
    > can figure out where you are, more or less, by trial and error from your
    > sight data. Go to the calculator on my web site, set the GMT of the sight to
    > 22:19:30 and set your DR Lat to 14d 31'N and your DR Lon to 61d 38.1W. That
    > nearly matches your sights, lunar and altitudes, too. So assuming your
    > observations were good (and I would bet they were) you were probably about
    > 30 miles west of Martinique. Does that fit your recollection?
    >
    > Now as it happens, this is yet another one of this miraculous lunar sights
    > where you can do the clearing without using any spherical trig. If we take
    > the pre-cleared altitudes and distance (the altitudes of the objects'
    > centers and the center-to-center lunar distance) and add them up, we get
    > nearly 180 degrees. So adjust the Moon's altitude higher by about 24 minutes
    > of arc and then work it AS IF they were exactly opposite each other in the
    > sky.
    >
    > �-FER
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