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    Re: LADEE Moon Probe Puzzle
    From: Robin Stuart
    Date: 2013 Sep 15, 12:08 -0700

    Bob,

    Nice write up and congrats on the very fine fix. In my calculation I did not go as far as accounting for the figure of the Earth as I was quite surprised and satisfied with my initial result which I and suspected might be somewhat fortuitous. It would seem from your analysis that this may not be the case.

    There are a few of additional effects that could be accounted for. The first is that I stated the burn out position in J2000.0 coordinates. These should be converted to the apparent position for the equinox of date and changes the direction of the rocket slightly. In those coordinates the Stage 3 burn out position is R.A. 23h 6m 34.2s, Declination -31d 41.6’ which moves my estimated position a bit to the South West and more in line with the rocket’s azimuth.

    In principle of course the local elevation which is around 75m should be accounted for. There is also some parallax induced by atmospheric refraction. Refraction means that the observer actually seeing rays that would pass over his head if atmosphere were removed. Due to the resulting parallax the rocket appears lower than its true geometric position with respect to the background stars. I believe that this phenomenon is something that needs to be accounted for in very precise eclipse timings,

    Regards,

    Robin Stuart

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