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    Re: Cones of Position, Lunars and the Apollo Sextant
    From: Ed Popko
    Date: 2019 Aug 4, 05:42 -0700


    This explanation helps a lot. Now I know the apex of the cone is the center of the moon (cleared lunar), a point I missed when first trying to visualize this. And yes, a diagram would certainly help.

    I'm guessing here. I assume the body (star or planet) and the observer are somewhere on the surface of this very large cone, as it radiates out in 3D space from the moon. Yes?  

    Unlike traditional CelNav where the cone's centerline intersects the body's Ground Point on earth, the centerline of the lunar's cone will never pass through the earth. And because the stars are so far away when compared to the moon'd distance from earth, that centerline will always point from the moon more than 90 degrees away from earth. And if I still have this right, the Circle of Position formed where cone intersects the moon's surface, would only be partially visible from earth because part of that COP is over the moon's horizon. But none of moon's COP is particularly useful to us since we are not on the moon to make use of it.

    Returning to earth, it's easy to see that the cone's 'diameter' is so large that the portion of it's surface that passes through the earth is a plane of all practical purposes. And that plane's intersection on earth scribes a LOP, the observer is on that LOP.

    Is any of this right so far?

    Some questions:

    1. Does the cone's surface also pass through the center of the earth as well as the observer?

    2. How does our assumed position on earth relate to this Line of Position (cone intersection at a given UT)?


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