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    Re: Home-built sextant
    From: W F Jones
    Date: 2014 Jan 08, 11:29 -0500

    Since it is now possible to 3D print (using metals) a 1911 semiautomatic
    pistol that appears to work rather well.  A traditional sextant could
    also be constructed in this manner.  I am amazed that all parts of the
    pistol, including screws and springs were printed, wow!  A simple
    internet search tells more...
    
    With 3D printing technology, metal components may be fashioned and
    optical elements may be molded or perhaps also printed.  Optical
    encoders for precision angular metrics are now commonplace.  A large
    assortment of fantastic sensors combined with electronic/computing
    circuits enjoy wide usage today.  Miniaturization has introduced terms
    such as nano and molecular into our vocabulary.  So in my opinion, it
    should be possible to build an inexpensive sextant that would have
    superior specifications to any sextant today.  Such a device might not
    give a mariner more confidence in his position but the resources are
    certainly out there.
    
    Why would you want to design, build or own one?  Most agree that no
    significant market exists today so the economics of such a venture isn't
    very attractive.  Even if 3D printing were used to lower the
    manufacturing costs who wants a navigation system known to be somewhat
    complex (except for NavList members) and impossible to use when seas are
    rough and the weather foul.
    
    If you could afford to modernize this device, why not consider an
    alternative that might deliver more while providing a better backup
    system for GPS.  Such a system is apparently in use but not available to
    the public and it may only work at high altitudes too.  So why not dream
    big and consider a multi-body tracking system that would operate during
    periods of good seeing whether night or day in a continuous manner.
    Even if only night operation is available, inertial guidance could
    fill-in when tracking fails during inclement weather or other
    disruptions.  It is likely that optical ring gyros are operational on
    many platforms today.  Would a system such as this actually give better
    positional information than the traditional methods?  I like to think so
    but that's another matter.  The goal to create a device that could
    compare favorably to the outdated LORAN system while providing global
    coverage would be useful if the cost is kept under $...
    
    My dear wife says I need to stop daydreaming and get on with some chores
    so you have my meager and not well thought out contribution.
    Regardless, no plans here to make a DIY/home-built sextant.
    
    Frank
    Rochester, NY
    
    On 1/6/2014 1:22 PM, Frank Reed wrote:
    > In another thread, Sean asked:
    > "how long before we see the first "3D printable sextant"?"
    >
    > This question was spawned by some humorous speculation about sextants being 
    outlawed which may have brought to mind some recent new stories about 
    homemade 3D printed handguns (not really viable at this time). But this is an 
    element of a broader question: could you build a reasonably accurate sextant 
    at home? Does 3D printing have anything like the required precision at this 
    time? Could we re-purpose some other components to create a really good 
    angle-measuring instrument?
    >
    > I'm sure some of you have seen a design, I think originally by Omar Reis, 
    that uses a CD case to provide a simple rotating base element. Adding a 
    couple of mirrors and a home-printed scale, you get a nice little sextant 
    with accuracy around a tenth of a degree if you're careful. Primitive but 
    usable. Can that design be improved upon?
    >
    > Could the pivot of a marine sextant be manufactured by any home "shop" 
    techniques, 3D printing or otherwise? How about some digital means of 
    producing scales? Would a vernier sextant be easier to produce than a 
    micrometer sextant?
    >
    > And what about a more mechanical sextant (similar to some aviation sextants) 
    using a gearbox and showing a "digital" readout for the angle? Could we 
    produce something small and very accurate? Fundamentally, a sextant is a very 
    simple device: it rotates one mirror with respect to another by a 
    pre-determined, readable angle, with high accuracy and repeatability. Surely 
    with some elements of modern computer-driven manufacturing, there's a way to 
    go beyond the traditional marine sextant design...
    >
    > -FER
    >
    >
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