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    Re: Difficult observations
    From: Greg Rudzinski
    Date: 2009 Nov 20, 10:13 -0800

    Ron,
    
    I find that when the batteries of my Mark 5 bubble go dead that
    looking off to the side a bit would help some and even placing the
    star outside of the bubble and tangent to the edge would get me in the
    ballpark. At sea on my sailboat the bubble can't be used so on the
    mark 5 the bubble is removed from view and the visible horizon feature
    is flipped into position thus converting to a standard sextant(no good
    on New Moon nights). Bubble sextants may not have had this option in
    the 30s for Noonan and AE.
    
    Greg
    
    On Nov 20, 9:51�am, Ronald P Barrett  wrote:
    > As a long time flight nav (old), I know from an aviation point of view, in 
    the weather, night, turbulent flying, star observations to be difficult, 
    especially with a hand held sextant as flown in the 30s and early 40s. Even 
    worse was a sextant with no averager! One great improvement that was so 
    simple: was the sky-hook. You could they hang onto the sextant and be 
    somewhat more stable in your effort to get a sighting. An even worse 
    condition was when the battery that supplied power to the bubble lamp went 
    dead... you were all but sunk! I often wonder if that was Amelia Earhart's 
    Nav-Noonan's problem on his long 20hr flight in to Howland Island. He had all 
    of the above "worse conditions." Ron Barrett, President Air Force Navigators 
    Observers Association (AFNOA)
    >
    > --- On Fri, 11/20/09, Anabasis  wrote:
    >
    > From: Anabasis 
    > Subject: [NavList 10767] Difficult observations
    > To: "NavList" 
    > Date: Friday, November 20, 2009, 11:17 AM
    >
    > ��� In the world of taking observations, as opposed to reducing them, I
    > was thinking of the observations that are the most difficult to shoot
    > at sea and thought that I�d make a short list.� I am wondering what
    > others might think and how they rate different observations in order
    > of observation difficulty.� I am not going to list such main stays as
    > sun lines, azimuths, and upper transits.
    > ��� By difficulty I mean to not only observe them, but to get useful
    > data.� In any case, here is the list of exotic sights that I�ve taken
    > in order of difficulty
    >
    > 1)��� High altitude sights of the moon (Ho >89 degrees)
    > 2)��� High altitude sights of the sun
    > 3)��� Amplitudes of stars/planets
    > 4)��� Amplitudes of the moon
    > 5)��� Nighttime (by moonlight) star fix
    > 6)��� Lower transit of a star (due mostly to low altitude)
    > 7)��� Lunar distances
    >
    > I�d be interested in hearing what other sights have proven troublesome
    > to navigators out there.
    >
    > Jeremy
    >
    > --
    > NavList message boards:www.fer3.com/arc
    > Or post by email to: NavList@fer3.com
    > To unsubscribe, email NavList+unsubscribe@fer3.com
    
    -- 
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
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