NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Difficult observations
From: Greg Rudzinski
Date: 2009 Nov 20, 12:54 -0800
From: Greg Rudzinski
Date: 2009 Nov 20, 12:54 -0800
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 Gebhartwrote: > 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 > > >> -- > >> NavList message boards:www.fer3.com/arc > >> Or post by email to: NavList@fer3.com > >> To , email NavList+@fer3.com > > > -- > > NavList message boards:www.fer3.com/arc > > Or post by email to: NavList@fer3.com > > To , email NavList+@fer3.com -- NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList+@fer3.com