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    Re: Working a lunar
    From: Paul Hirose
    Date: 2009 Aug 02, 15:13 -0700

    Antoine wrote:
    > So, my results would not be that bad ...
    
    Your results are only 1 second different from my program.
    
    But it recommends the upper limb of the Moon, because the light is
    coming from almost directly above (position angle = 350°). Of course, if
    the "observation" was calculated, this doesn't matter. Even if it was
    really observed, I don't think there is much error because the Moon is
    nearly full (phase angle = 4°), and the cleared lunar distance is not
    very sensitive to altitude.
    
    My corrected time is 2001-04-08 at 03:21:10.5 UT1 (03:22:14.5
    Terrestrial Time). Position fix from the altitude observations is
    N44°50.48' W011°01.08'.
    
    I checked the solution by entering the Terrestrial Time, latitude, and
    longitude W11°17'07.2" into the USNO MICA 2.0 program. Longitude equals
    my solution, moved west by delta T (64 seconds) converted to arc (= 64 *
    15 * 1.002738 arc seconds). With these inputs, the outputs from MICA
    should match the observations. (MICA does not compute refraction, so I
    used my program's values.)
    
      31.4506  Moon altitude
      - .2718  semidiameter
      + .0263  refraction
    ---------
      31.2051  lower limb (calculated)
      31.2050  lower limb (observed)
    
      17.7536  Mars center
      + .0497  refraction
    ---------
      17.8033  refracted center (calculated)
      17.8033  refracted center (observed)
    
      64.9266  refracted separation angle
      + .2718  Moon semidiameter
    --------
      65.1984  lunar distance (calculated)
      65.1983  lunar distance (observed)
    
    The check is good.
    
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