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    Re: US Naval Academy reinstates classes in celestial navigation
    From: Bill B
    Date: 2015 Oct 25, 21:38 -0400

    On 10/24/2015 7:02 PM, Sean C wrote:
    > All,
    >
    > Attached are the teaching aid graphics I made for Rommel. I'm posting
    > them here in case anyone else might be able to get some use out of them.
    > Enjoy!
    
    Sean
    
    Nicely done. A step 2 instead of step 1, step 3 then step 3. Much
    clearer than the original. ;-)
    
    Under the category of "Everyone is a critic," there are some issues with
    the original blog graphic that remain unresolved for me in your artful
    renditions.
    
    1. The position of the sun in the scope. You corrected the original
    debatable decision to align the center of the sun with the (not visible)
    horizon. The horizon is centered vertically in the scope's FOV--great.
    But...the sun far to the right of the scope's center may reduce accuracy.
    
    2. Which brings me to my pet peeve. It is clearly a traditional mirror
    with a lower-power scope as opposed to higher magnification scopes or a
    whole horizon mirror. Unless the scope has been poorly adjusted
    laterally, the viewer will not see squat if the sun is off the "magic
    spot" we take for granted.
    
    Borrowing from Ken G describing what a sextant does, "It measures
    angles." Anything past that for a booth visitor looking through a
    sextant while holding it upside down was superfluous. The next important
    step after turning the sextant right side up in introducing a newbie to
    sextant use is IMHO--and borrowing from firearm jargon--the sight picture.
    
    With iron sights you align the front sight to the rear sight and the
    target until it looks like the provided diagram of a sight picture. That
    is similar to to the approach I use with someone who has never looked
    through a sextant scope before. I've done it in the rain with a broad
    building, a lighthouse then a natural water horizon. Set the sextant a
    few degrees or so off alignment for the target and ask them to locate
    the spot where they see ghost images on two sides. Now turn the
    micrometer drum until the ghost images overlap exactly.
    
    Which may be the long road to my point, but I feel without illustrating
    the overlapping diminishing-transparency horizon and index images it
    leaves the reader or student like a male dog with a full bladder between
    four trees--not a leg to stand on. Or illustrate whole horizon mirror.
    
    I understand I'm being picky, but when introducing a concept to someone
    who is tabula rasa, I put myself in their place, remembering when I
    first learned. What I take for granted now may well be uncharted
    territory for the student.
    
    Keep up the good work.
    
    
    

       
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