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    Re: Swinging the Arc
    From: Tom Sult
    Date: 2012 Aug 17, 17:46 -0500

    The graphic is nice but shows the sun being brought down below the horizon and 
    lifted. This would give backlash error.
    
    Thomas A. Sult, MD
    Sent from iPhone
    
    On Aug 17, 2012, at 16:26, bill  wrote:
    
    > Indeed a nice graphic. It did appear the sextant was swung about the axis of 
    the scope. I followed a link provided in the site to their sextant article
    >
    > http://en.wikipedia.org/wiki/Sextant
    >
    > which stated, " 'Swinging' the sextant about the axis of the telescope 
    ensures that the reading is being taken with the instrument held vertically."
    >
    > This raises the old topic of whether the sextant should be swung about the 
    axis of the scope, or axis of the observer to the body?
    >
    > If I recall the consensus was axis of observer to body. As I cannot walk and 
    chew gum simultaneously, I have never quite figured out how to achieve that 
    goal.
    >
    > I spent considerable time attempting the technique in my last round of 
    observations from a pier on Lake Michigan using the Sun, Moon, Mars, Saturn 
    and Spica. I did better on my very first beginner's round of sights using the 
    home-built cardboard sextant from Celestaire from a 34' sailing craft!
    >
    > My intercepts from the pier ranged from 4!7'away for the Sun to 17'+ away 
    for the Moon. Standard deviations were into multiple minutes, while my SD 
    norm from land is 0!3 or less. On average, observations were an order of 
    magnitude worse than my norm, and always away.
    >
    > So much for theory, at least as I practice it ;-)
    >
    > If anyone has a "Swinging the Arc for Dummies" article, I would love to read it.
    >
    > Bill B
    >
    >
    > On 8/17/2012 3:45 PM, Hewitt wrote:
    >> Here's a nice brief graphic of using the sextant. First one I've run
    >> across showing things in motion.
    >>
    >> Hewitt
    >>
    >> Sent from my iPad
    >>
    >> Begin forwarded message:
    >>
    >>> *From:* Hewitt >
    >>> *Date:* August 17, 2012 12:31:23 PM PDT
    >>> *To:* "hhew36@gmail.com " >> >
    >>> *Subject:* *File:Using sextant swing.gif - Wikipedia, the free
    >>> encyclopedia*
    >>>
    >>> http://en.wikipedia.org/wiki/File:Using_sextant_swing.gif
    >>>
    >>>
    >>> Sent from my iPad
    >
    >
    >
    >
    
    
    
    

       
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