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    Re: Errors in USNO celestial data
    From: Antoine Couëtte
    Date: 2010 May 3, 06:26 -0700

    Dear Douglas,

    You wrote


    Is it too simple to just enter a date/time 5.3 s earlier than the observation? or am I missing something?


    Although I am not familiar with ICE, I would guess that if you enter a " date/time 5.3 s earlier than the observation ", then you will compute both RA and Dec for the correct TT (was called TDT then ...) as related to your "target UT". But for this " date/time 5.3 s earlier than the observation " you will get GMST/GAST value for "target UT - 5.3s" rather than for your "target UT".

    Since you can not modify delta T, you need to compute RA and D with your method. But it will not give you the correct GHA values, since GAST would not be computed at the time you would need it.

    Hope it can help you.

    And of course, if I am totally off track, let some charitable soul put me back onto the right track.

    Antoine M. "Kermit" Couëtte

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