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    Re: Errors in USNO celestial data
    From: Douglas Denny
    Date: 2010 May 3, 02:14 -0700

    Hello Antoine.

    I am not sure of what you are suggesting. All calculations using ICE are within the programme; including GST based on an input of UT.

    What is required is for the algorithm within the programme to be using a dynamical time for all calculations which is correct for the instant of the actual observation - which is of course the measured UT (deck-watch time).

    Normally one inputs UT and the programme uses a delta T within to correct to Dynamical Time, and I assume ICE does this first, then makes all calculations for the data sets including GST (Aries) from that.

    ICE gives an output which including Aries GHA for all the navigational computations made, so it must be from the basis of UT provided, then a delta T correction within as above.

    I still cannot see that my suggested correction needs any more than an adjustment to UT at input for all or any of the ICE 'outputs'.

    For example: for 2010 the programme uses a delta T of 71.8 sec. but the correct delta T should be 66.5 s. Is it too simple to just enter a date/time 5.3 s earlier than the observation? or am I missing something?

    Douglas Denny.
    Chichester. England.
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