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Ken,

Maybe the bubble sextant I have isn't a mark 5. The numbers on the
bottom are AN-5851-1. The lighting is powered by 2 D batteries. The
magnification seems to be 2X and I can observe the body in the center
of the bubble as well as adjust the bubble to any desired size. The
unit also has a two minute averager and a ring to hang on a dome hook.
There is also a holder for an Elgin stop watch on the bottom.

Greg

On Nov 20, 12:32�pm, Ken Gebhart  wrote:
> Greg,
>
> There is no electrical lighting of the bubble in the Mark 5, so why �
> should that make a difference? �Also, (if we are talking about the �
> Navy Mark V) the body SHOULD be placed outside, and alongside of the �
> bubble. �It is an opaque bubble, not designed to be looked through. �
> Although it is tempting.
>
> Ken Gebhart
> On Nov 20, 2009, at 7:13 PM, Greg Rudzinski wrote:
>
> > 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
>
> >> --
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>
> > --
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