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    Re: Sextant certificates
    From: Fred Hebard
    Date: 2006 Feb 2, 10:15 -0500

    Jim,
    
    It might be helpful to add a column for Ho to these data, to see
    whether there is any dependence for Hc-Ho.  This would suggest the
    occurrence of arc errors such as are shown on sextant certificates.
    
    Fred
    
    On Feb 2, 2006, at 10:02 AM, Jim Hickey wrote:
    
    > Alex it is interesting that a certificate would show a 10" error
    > over the whole arc! I guess a simple IC of 10" would take care of
    > that! What was your experience like having the sextant checked by
    > Freiberger?
    >
    > Ken thanks for your comments re: managing errors <1'. I haven't dug
    > into this issue the way you suggest but have kept some data I have
    > been collecting to get an idea of sextant/observation performance
    > that I have listed below.
    >
    > I kept this data as it took a few of the variables out like
    > bouncing on the boat, odd horizon conditions etc. So, to me, the
    > results represent the upper end of performance that I might expect
    > with single shots. No question more statistics sheds more light on
    > the issue. Good challenge trying to track down those <1' instrument
    > errors.
    >
    > - These are differences in minutes of angle between Hc and Ho,
    > approximate position being GPS position
    > - Mostly star sights
    > - Taken at different times over the past year or so
    > - All taken with an artificial horizon
    > - All taken under ideal conditions i.e. calm clear
    > - No averaging or plotting
    >
    > 0.4
    > 0.3
    > 0.4
    > -0.4
    > -0.5
    > 0.2
    > 0.1
    > 0.1
    > -0.1
    > 0
    > -0.2
    > 0.1
    > -0.4
    > 0.2
    > -0.1
    > 0.4
    > -0.3
    > 0.3
    > 0.1
    > 0
    > -0.1
    > 0.3
    > 0.1
    > -0.1
    > -0.3
    > 0.1
    > 0.4
    > -0.2
    >
    >
    
    
    

       
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