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    Re: Sextants
    From: Dan Allen
    Date: 1999 Jul 27, 11:59 AM

    I started with the cheap Davis Sextant ($27.50) and it has not been great: 
    screws have fallen out and made it unusable.  I next bought an Astra IIIb 
    ($450) and it feels like a quality piece of gear, and I'd recommend getting 
    an Astra.  You will take things more seriously because you can measure angles 
    more accurately and before you know it you will actually be using the thing a 
    lot to see how good you can get at determining your location, and voila, you 
    will have become proficient!
    
    I never invested enough time, effort, thought, and energy to get the hang of 
    celestial nav with just the cheap plastic sextant.
    
    Better than buying a Celesticomp, try writing your own software as a way of 
    learning the math behind celestial navigation.  Use Visual Basic, VBA in 
    Excel, C, or Perl, or Awk, or JavaScript, or any other programming language 
    laying around, and write your own computational software.  It will be a great 
    education and again, you will know and understand things when you are done.
    
    If you have done these things, then when you really need to rely upon them -- 
    when your Garmin GPS dies (like mine has!) -- then you will not be flustered 
    or panic because you will know how to use your sextant as if it was second 
    nature.
    
    A bit more than a week ago we finally saw the sun long enough up here in 
    Washington state that I again went out and repeated my experiment as follows:
    
    1) Measure my back porch with a Garmin GPS III in average mode so I get my 
    location to within about fifty feet...
    
    2) Use a Davis artificial horizon and do a line of shots of the sun over an hour, taking many readings.
    
    3) Plug in my sitings to my own software and see how close I can get.
    
    I did it with my Tamaya Jupiter sextant and my new C. Plath Navistar 
    Professional, and with the Plath I got my most accurate shots yet: 0.04 nmi 
    (243') was my best and the whole series had a mean error of .108 nmi (656')!
    
    I finally feel proficient at this stuff, but it has taken time and effort.  
    Anything worth doing always does take time and effort.
    
    Dan Allen
    danallen{at}microsoft.com
    
    -----Original Message-----
    From  Barry Colman [mailto:delta611{at}EARTHLINK.NET]
    Sent: Tuesday, July 27, 1999 6:31 AM
    To: NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM
    Subject: Sextants
    
    
            Im a beginning Celestial Navigator and am seeking some
    advise...I have access to a Davis MK25 Sextant to learn with..or
    SHould I purchase the Astra IIIb to learn with..?? I don't plan any
    crossing in the immediate future...One other thing, I was also
    thinking of purchasing the Celesticomp V for checking my math and
    learning with it. or should I pass on the puter to learn the
    conventional way....
    
                                    Thanks
    
                                            Barry
    
    P.S. If this has been discussed before I apologize, I cant find an
    archive..!!
    

       
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