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    Re: Celestial Navigation without a sextant.
    From: Gary LaPook
    Date: 2008 Mar 12, 03:19 -0700

    Gary LaPook writes:
    
    Your discussion reminded me that I used to use this technique from time
    to time for practice. I just looked in my wallet and found the little
    table I had prepared for this and which has been tucked under my pilot's
    license for more than thirty years. I have attached a scan of it . This
    table combines dip and refraction for all bodies (first column) plus
    semi diameter for the sun (lower and upper limb, second and third
    columns) when the body is on the horizon as observed from various flight
    altitudes and so gives the Ho of the observation. (all Ho's are
    negative.) I remember that I was impressed by the accuracy of using this
    table in flight ( compared to the usual level of accuracy of in flight
    cel nav, not to the standard of marine navigation) but I don't have any
    numbers to give you since it has been a long time since I used this table.
    
    
    gl
    
    
    frankreed{at}HistoricalAtlas.net wrote:
    
    >Jim writes:
    >"In his chapter "Celestial Navigation Without a Sextant" he has a worked
    >example using the sun as it sets which he claims "the LOP produced agreed
    >exactly with the distance run since a fix made earlier by advancing sun
    >lines"."
    >
    >Sometimes ya get lucky! It might be fun to try this ten days in a row and
    >see how well it works on average.
    >
    >And:
    >"I haven't tried this type of sight myself but was always a little curious
    >to try it."
    >
    >Supposedly, Nathaniel Bowditch himself experimented with these sextant-free
    >sights on his first ocean voyage in 1795 but abandoned them. In his case,
    >though, I think he was trying to observe the rising and setting of stars.
    >Since he had never been to sea before, he apparently did not know that this
    >was basically impossible. And since they had no chronometer, the value of
    >these sights was minimal anyway.
    >
    > -FER
    >
    >
    >>
    >
    >
    >
    
    
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