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    Re: 18 june 2013 lunar distance
    From: Paul Hirose
    Date: 2013 Jul 01, 11:53 -0700

    I wrote:
    >>For 18 June 2013 at 3:30:00UT1, geocentric lunar distance to Altair:
    >
    > USNO MICA 2.0
    > 106 34 28.48 (= 106 34.4747), calculated from geocentric apparent places
    > with respect to true equator and equinox at TT = 03:31:07.1.
    >
    > 12 49  1.478  -8 12 48.78  Moon
    > 19 51 28.291  +8 54 23.41  Altair
    
    I should have explained that a flaw in MICA 2.0 makes it impossible to
    realize the full accuracy of the program if one uses UT1 to compute Moon
    coordinates. At 03:30 UT1 MICA says:
    
    12 49  1.557  -8 12 49.17
    
    With that position the separation angle from Altair is 106 34 27.36 (=
    106 34.4561), 1.1″ less than from the value quoted above. The reason is
    that MICA thinks delta T is 69.289, but it's really 67.118. There is no
    provision for manual input. Thus for best accuracy one must convert
    03:30:00 UT1 to 03:31:07.1 TT and select the TT scale in MICA.
    
    I think MICA 2.0 uses the JPL DE405 ephemeris. I don't have a DE405 file
    on hand, but DE406 is the same integration in a more compact storage
    format. In this case there's practically no difference between DE406 and
    the recent DE422 ephemeris. RA is .001 s different, declination
    identical at 0.01″ precision.
    
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