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    Re: Open Cockpit Sun Sights Exercise
    From: Gary LaPook
    Date: 2013 Mar 6, 14:14 -0800
    A 6 NM intercept is good work and within the normally expected level of accuracy for a sextant shot in flight. The accepted level of accuracy for in flight fixes is 10 NM which requires the individual sights to be within 7 NM. Good work.

    I use a GPS device that records its position every five seconds and use the coordinates that it puts in an output file for the actual position to compare with the sextant shot LOP.


    The file can also be used to draw the flight path on Google Earth as was done on the images attached to :


    Here are links to you tube videos of me using an MA-2 and an A-7  in flight and also an astrocompass:




    I was flying the plane and taking the shots at the same time, no autopilot, and the results were one shot 6 NM towards and the other 6 NM away. I was solo in the Cessna Skycatcher, C-162.



    --- On Wed, 3/6/13, Ken Gebhart <gebhart@celestaire.com> wrote:

    From: Ken Gebhart <gebhart@celestaire.com>
    To: garylapook@pacbell.net
    Date: Wednesday, March 6, 2013, 1:07 PM

    Paolo, It sounds like you had the back seat person hold the plane steady while you averaged readings over a period of time. Averaging would be necessary because the control inputs necessary to hold the plane steady impart accelerations to the bubble.  You might try next time to take a single sight while the plane is trimmed hands off. Between the beginning and end of the sight, if the plane did not change heading or speed, the sight should be accurate. Of course I don't know if you CAN trim a Stearman hands off!

    On Mar 6, 2013, at 2:14 AM, Paolo Borchetta wrote:

    This morning I took a pilot friend and we went flying to take a series of sun' sights and see the results. The plane, a Boeing Stearman, is an open cockpit biplane of the late 30's, I sat in the front cockpit which is a bit more spacious and allows me to be able to get shots looking on one side thus clearing the upper wing.
    The session was rough one in terms of just taking a series of sights, mathematically averaging them, the same for the time, start of series UT and end of series UT, averaged. Few calculation on a knee board piece of paper to get a single LOP. Not much use but later the data have been verified against the USNO results for same position and time. Here are results:
    Ho 46 09.4' against a Hc 46 15.8' with an intercept of 6.3'A.
    bubble octant A-12 Link, bubble size 2.5 sun' dia.,pressure altitude 5,000 feet, speed 75 Knots and OAT 16C. Pos. Lat 24 28.2'N; Lon 054 22.8'E.
    The old Links still works.....

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