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    Re: Star Fix statistics
    From: Jeremy C
    Date: 2009 Sep 23, 20:49 EDT
    I have a bar graph of all of the fixes and you can certainly tell when the horizon was poor.  We had fairly good weather most of the time.  The only time the "weather" rather than the horizon was an issue was during one AM twilight when we had Force 8 wind and seas in the South Indian Ocean.  Getting the stars that morning wasn't as fun as usual.
     
    I used the C. Plath for one set of stars when the cadet was using my mainstay, a Tamaya.  It was wonderfully accurate (0.1nm fix error) but i had a heck of a time FINDING the stars.  They didn't pop into view like the Tamaya does with the 7x scope (The Plath has a 4x40).  I couldn't shoot my usual round of six or seven bodies.
     
    The IE changed from 0.8 to 1.2 on the arc about 2/3 of the way.  I hesitated but my intercepts and lunars pointed to a slightly greater error, so i took the plunge and changed it.  The results were better.
     
    I wear that ironman everywhere on the ship and never off of it.  It sure has done me well for the last 2 years.  My previous "wal-mart specials" have done about as well.  It goes to show if you spend $30 instead of $17, you get a better rate ;-)
     
    One stat I forgot was the average number of LOP's per fix.  I ranged from 2 to 17 I think.  I will have to look that up later.
     
    Jeremy
     
    In a message dated 9/23/2009 7:08:23 P.M. Eastern Daylight Time, gregrudzinski@yahoo.com writes:

    Jeremy,

    Really good shooting! It would be interesting to know how rough
    weather observations and less than good horizon conditions compared to
    the average. That Timex Ironman of yours is way better than average
    and should be kept in the sextant box for CN only. Did you use the
    same sextant for all the shots and was index error constant throughout
    the trip?

    Greg



    On Sep 23, 3:40 pm, Anabasi...@aol.com wrote:
    > I shot 70 star fixes on my trip from Japan to the USA and here are a few  
    > interesting statistics.
    >
    > 1) average fix error from GPS: 0.566 nm  (low of 0.0 and high of 2.7  nm
    > error)
    >
    > 2) 88.6% of the fixes were under 1.0 nm fix error.
    >
    > 3) 60.0% of the fixes were under 0.5 nm fix error
    >
    > 4) two fixes had errors under 0.05 nm (under 100 meters).
    >
    > My next project is to determine the average intercept based on the GPS fix  
    > as the DR but that is over 700 data points so might be awhile.
    >
    > Jeremy --~--~---------~--~----~------------~-------~--~----~
    NavList message boards: www.fer3.com/arc
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